A

abundant number (4) A number in which the sum of all its proper factors is greater than the number itself.

Example: 12 is an abundant number because the sum of its proper factors
is 1 + 2 + 3 + 4 + 6 = 16 and 16 is greater than 12.

acre (4) A unit of area. A commonly used measure of land that can be any shape provided it equals 43,560 square feet.

acute angle (4) An angle greater than 0 degrees and less than 90 degrees. See angle.

addition A mathematical operation based on "putting things together." Numbers being added are called addends; the answer is called the sum. In 12 + 33 = 45, 12 and 33 are addends, and 45 is the sum. Subtraction "undoes" addition: 12 + 33 = 45; 45 - 12 = 33, and 45 - 33 = 12.

algorithm (3) A set of step-by-step instructions for doing something — carrying out a computation, solving a problem, and so on.

analog clock (1) A clock that shows the time by the positions of the hour and minute hands. A digital clock shows the time as digits in hours and minutes, with a colon separating the two.

angle (1) A figure consisting of two rays with the same endpoint. The endpoint is called the vertex of the angle. An acute angle has a measure greater than 0° and less than 90°. An obtuse angle has a measure-ment greater than 90° and less than 180°. A right angle has a measurement of 90°. A straight angle has a measure of 180°.

angles, adjacent (4) Two angles with a common side, the same vertex, and that do not overlap. In the diagram, angles 1 and 2 are adjacent angles. So are angles 2 and 3, angles 3 and 4, and angles 4 and 1.

angles, vertical (4) Two angles with the same vertex, but no sides in common. In the diagram, angles 2 and 4 are vertical angles. They have the same vertex but no sides in common. Their measures are equal. Similarly, angles 1 and 3 are vertical angles.

apex (3) In a pyramid, the point at which all faces except the base meet.

area (2) The measure of the amount of surface inside a closed boundary.

array (K) A rectangular arrangement of objects in rows and columns.

attribute (K) A common feature (size, shape, color, number of parts, and so on) of items in a set.

average (mean) (3) A typical or middle value for a set of numbers. It is found by adding the numbers in the set and then dividing the total by the number of values in the set.

Example: 2, 4, 5, 9, 10 = 30; 30 ÷ 5 = 6; The mean is 6.

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B

bar graph (1) A graph in which horizontal or vertical bars represent data.

base of a polygon (4) The side on which the polygon "sits;" the side that is perpendicular to the height of the polygon.

base of a polyhedron (1) The "bottom" face of a polyhedron; the face whose shape is the basis for classifying a prism or pyramid.

C

capacity (3) A measure of how much liquid or other pourable substance a container can hold.

Celsius (K) A scale for temperature measurement where water freezes at 0° C and boils at 100° C.

centimeter (cm) (1) In the metric system, a unit of length equivalent to 10 millimeters, of a decimeter, or of a meter.

chance (4) The possibility of an outcome in an uncertain event.

Example: In tossing a coin there is an equal chance of getting heads or tails.

circle (4) The set of all points in a plane that are a given distance (the radius) from a given point (the center of the circle).

circle pie graph (3) A graph that uses a circle divided into parts to show the parts of a set of data. The circle represents the whole set of data.

circumference (3) The distance around a circle or sphere.

column (1) A vertical arrangement of objects or numbers in an array or table.

compass (4) a) A device for drawing circles. b) A navigational device that points to Earth's magnetic North Pole.

composite number (4) A whole number that has more than two factors. A composite number is divisible by at least three whole numbers.

Example: 10 is a composite number because it has more than
two factors: 1, 2, 5, and 10.

concave polygon (4) A polygon in which at least one vertex is "pushed in". Also called nonconvex.

concentric circles (4) Circles that have the same center but radii of different lengths.

cone (1) A 3-dimensional shape having a circular base, curved surface, and one vertex.

congruent (4) Two figures that are identical—the same size and shape—are called congruent figures. If you put one on top of the other, they would match exactly. Congruent figures are also said to be congruent to each other.

context (2) Setting; what the numbers represent. Numbers nearly always have a context, such as four pancakes or twelve inches. Also called “units.”

convex polygon (4) A polygon in which all vertices are “pushed out.”

coordinate (3) A number used to locate a point on a number line, or either of two numbers used to locate points on a coordinate grid.

coordinate grid (3) A device for locating points in a plane by means of ordered number pairs or coordinates. A rectangular coordinate grid is formed by two number lines that intersect at right angles at their 0 points.

counting on (K) Adding by counting from a specified number.

Example: 5 + 2 would sound like "5, 6, 7"

cube (1) A polyhedron with six square faces.

cube a number (4) The product of a number used as a factor three times.

Example: The cube of 5 is 5 x 5 x 5, or 125. Also written as 5³.

cubic centimeter (cm³) (4) A metric unit of volume; the volume of a cube 1 centimeter on a side. 1 cubic centimeter is equal to 1 milliliter.

cubic unit (3) A unit used in volume and capacity measurement.

cubit (1) An ancient unit of length, measured from the point of the elbow to the end of the middle finger; between 18 and 22 inches.

customary system of measurement (1) The measuring system used most often in the United States. Units for linear measure (length, distance) include inch, foot, yard, and mile; units for weight include ounce and pound; units for capacity (amount of liquid or other pourable substance a container can hold) include cup, pint, quart, and gallon.

cylinder (K) A 3-dimensional shape having a curved surface and parallel circular bases that are the same size. A can is a common object shaped like a cylinder.

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D

data (1) Information gathered by observation, questioning, or measurement.

deca- Prefix meaning ten.

decimal A number written in standard notation, usually one containing a decimal point, as in 2.54.

decimal point (2) The period which separates the whole number from the fraction in decimal notation. In expressing money, it separates the dollars from the cents.

decimeter (dm) (3) In the metric system, a unit of length equivalent to 10 centimeters or of a meter.

deficient number (4) A number in which the sum of all its proper factors is less than the number.

Example: 10 is a deficient number because the sum of its proper factors is 1 + 2 + 5 = 8 and 8 is less than 10.

degree (°) (1) a) A unit of measure for angles; based on dividing a circle into 360 equal parts; b) A unit of measure for temperature.

denominator (1) The number of equal parts into which the whole (or ONE or unit) is divided. In the fraction , b is the denominator or the number written below the line.

diagonal (1) An arrangement of objects or numbers from upper left to lower right or from lower left to upper right in an array or table.

diameter (3) A line segment that passes through the center of a circle (or sphere) and has end-points on the circle (or sphere); also, the length of such a line segment. The diameter of a circle is twice its radius.

difference (1) The amount by which one number is greater or less than another.

digit (1) In the base-10 numeration system, one of the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. Digits can be used to write any number.

Example: The numeral 145 is made up of the digits 1, 4, and 5.

digital clock (1) Clock that uses numbers only to show the time in hours and minutes, with a colon used to separate them.

dimension (4) A measure in one direction, for example length or width or height.

dividend (4) In division, the total to be divided by the divisor. See division.

divisibility test (4) A test to determine whether a whole number is divisible by another whole number, without actually doing the division. For example, to tell whether a number is divisible by 3, check whether the sum of its digits is divisible by 3.

Example: 51 is divisible by 3 since 5 + 1 = 6, and 6 is divisible by 3.

divisible by (4) One whole number is divisible by another whole number if the result of the division is a whole number with a remainder of zero.

Example: 28 is divisible by 7, because 28 divided by 7 is 4 with a remainder of zero

division (2) A mathematical operation based on "sharing" or "separating into equal parts." The dividend is the total before sharing. The divisor is the number of equal parts or the number in each equal part. The quotient is the result of division. The remainder is the number left over when a set of objects is shared equally or separated into equal groups.

Example: In = 4R1, 29 is the dividend, 7 is the divisor, 4 is the quotient and the remainder is 1.

divisor (4) If a number n is divisible by a number x, then x is a divisor of n.

Example: 21 is divisible by 3, so 3 is a divisor of 21.

doubles fact (1) The addition and multiplication facts without turn-around partners. A doubles fact names the sum or product of a 1-digit number added to or multiplied by itself.

Example: Addition: 4 + 4 = 8. Multiplication: 3 x 3 = 9

ABCDEFGHIJKLMNOPQRSTUVWXYZ

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E

endpoint (2) a) The point at either end of a line segment. Endpoints are used to name line segments. b) The point at the end of a ray.

Example: Segment TL or segment LT names a line segment between and including points T and L.

equidistant marks (1) Marks equally distant from one to the next along a line segment.

equilateral triangle (3) A triangle in which all three sides are the same length.

equivalent fractions (3) Fractions that have different numerators and denominators but name the same number.

Example: and are equivalent fractions.

equivalent names (1) Different ways of naming the same number.

Example: 2 + 6, 4 + 4, 12 - 4, 18 - 10, 100 - 92, 5 + 1 + 2, eight, VIII, and |||| ||| are some of the names for 8.

estimate (1) A calculation of a close, rather than exact, answer; a "ballpark" answer; a number close to another number.

even number (1) A whole number such as 2, 4, 6, and so on that can be evenly divided by 2 (divided by 2 with 0 remainder).

exponential notation (4) A shorthand way of representing repeated multiplication of the same number. In the example below the small raised 3, called the exponent, indicates how many times the number 2, called the base, is used as a factor.

Example: 2³ is exponential notation for 2 x 2 x 2.

extended fact (3) A number sentence obtained by multiplying numbers in a basic fact by 10, 100, and so on. Knowing 5 + 8 = 13 makes it easy to find 50 + 80; knowing 6 x 7 = 42 makes it easy to find 6 x 70.

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F

face (1) A flat surface on a 3-dimensional shape.

fact (basic fact) (1) Any of the simple number sentences that are the basis of all computation.

The basic addition facts are 0 + 0 = 0 through 10 + 10 = 20;
the basic subtraction facts are 0 - 0 = 0 through 20 - 10 = 10;
the basic multiplication facts are 0 x 0 = 0 through 10 x 10 = 100;
the basic division facts are 0 ÷ 1 = 0 through 100 ÷ 10 = 10.

Turn-around facts are pairs of related facts such as 3 x 5 = 15 and 5 x 3 = 15.

fact family (1) A group of addition or multiplication facts together with the related subtraction or division facts.

Example: 5 + 6 = 11, 6 + 5 = 11, 11 – 5 = 6, and 11 – 6 = 5 form a fact family;
5 x 7 = 35, 7 x 5 = 35, = 5, and = 7 form a fact family.

fact triangle (1) Triangular card labeled with the numbers of a fact family for practice with addition/subtraction and multiplication/ division facts. The two one-digit numbers and their sum or product (marked with an asterisk) appear in the corners of the triangle.

factor (verb) (2) To factor a given number is to find the values that multiple together to give you the original number.

Example: Factor 24
Possible answers: 6 x 4 = 24 3 x 8 = 24
1 x 24 = 24 2 x 3 x 4 = 24

factor (noun) (2) Any numbers that are multiplied together. Factors may be whole numbers, fractions, or decimals.

Example: 4, 3, and 2 are factors in 4 x 3 x 2 = 24; 0.5 and 25 are factors in 0.5 x 25 = 12.5; and 9 are factors in x 9 = 4 ; and -2 and -5 are factors in - 2 x (-5) = 10.

factor pair (4) Two factors of a number n whose product is the number n. A number may have more than one factor pair.

Example: The factor pairs of 21 are 1 and 21 and 3 and 7.

factor rainbow (4) A way of showing factor pairs in a list of all the factors of a number. This can be helpful in checking whether a list of factors is correct.

factor string (4) When a number is named by at least two factors. In the example, the factor string has three factors, so its length is 3. The number 1 may not be used in a factor string.

Example: A factor string for the number 24 is 2 x 3 x 4.

Fahrenheit (1) The temperature scale in which 32 degrees is the temperature at which water freezes; 212° is the temperature at which it boils.

fair (4) A coin or die is said to be fair if, over a large number of tosses, the results are consistent with the predictions of probability. Heads and tails should come up about equally often; the six sides of a die should come up equally often.

foot (ft) (1) In the U.S. customary system, a unit of length equivalent to 12 inches or of a yard.

formula (4) A general rule for finding the value of something. A formula is often written in abbreviated form with letters called variables.

Example: A formula for distance traveled can be written as d = r * t, where the variable d stands for distance, r for speed, and t for time.

fraction (1) A number in the form or a/b, where a and b are whole numbers and b is not 0. Fractions are used to name part of a whole object, part of a whole collection of objects, to compare two quantities, or as the quotient of a divided by b.

Frames and Arrows (1) Diagrams to represent number sequences—sets of numbers ordered according to a rule. The dia-grams consist of frames in which num-bers are written and arrows that apply the rules for moving from one frame to another.

frequency (2) The number of times an event or value occurs in a set of data.

frieze pattern (4) A design made by repeating one or more shapes along a strip by reflections, rotations, and or translations (slides).

fulcrum (1) The center support of a pan balance or other lever.

function machine (1) A diagram of an imaginary machine programmed to process numbers according to a certain rule. A number is input into the machine and is transformed into a second number (output) through the application of a rule.

ABCDEFGHIJKLMNOPQRSTUVWXYZ

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G

geometric solid (4) A 3-dimensional shape bounded by surfaces. Common geometric solids include the rectangular prism, square pyramid, cylinder, cone, and sphere. Despite its name, a geometric solid is "hollow;" it does not include the points in its interior.

girth (3) The measure around an object.

H

height of a parallelogram (4) The shortest distance between the base and the side opposite the base.

height of a triangle (4) The shortest distance between the base and the vertex opposite the base.

hemisphere (4) Half of a sphere. See sphere.

heptagon (1) A 7-sided polygon.

hexagon (1) A 6-sided polygon.

Home Link (K) A math activity intended to provide follow-up and enrichment at home.

I

image (4) The reflection of a picture or object that you see when you look through a transparent mirror. See transparent mirror.

improper fraction (4) A fraction that names a number greater than or equal to 1. A fraction whose numerator is equal to or greater than its denominator.

Example: , , , are improper fractions.

inch (in) (1) In the U.S. customary system, a unit of length equivalent to of a foot.

inequality (K) A number sentence stating that two quantities are not equal, or might not be equal. Relation symbols for inequalities include: (not equal), < (less than), > (greater than), (less than or equal), (greater than or equal).

Example: 3 < 10; 2 + 5 4 + 4

integer (4) Any whole number or its opposite.

Example: -2, 2, 6, -100 are examples of integers.

intersect (3) To meet (at a point, line, and so on).

inscribed polygon (4) A polygon is said to be inscribed in another figure if the vertices of the polygon lie on the other figure.

irregular polygons (1) Polygons with sides of different lengths.

isosceles triangle (4) A triangle in which two of the three sides are the same length.

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K

kite (1) A quadrilateral with exactly two pairs of adjacent congruent sides. (A rhombus is not a kite.)

L

latitude (4) A measure (in degrees) of how far north or south of the equator a location is on Earth; determined by circles of latitude parallel to the equator.

line (3) The extension of a line segment forever.

line graph (3) A graph in which points used to represent data are connected by a line or line segments.

line of reflection (mirror line) (4) A line halfway between a picture or object (pre-image) and its reflected image.

line of symmetry (2) A line through a symmetric figure. Each point in one of the halves of the figure is the same distance from this line as the corresponding point in the other half. That is, a line that divides a figure into two parts, with each part the exact mirror image of the other.

line plot (4) A sketch of data in which check marks, X's, or other marks above a number line show the frequency of each value.

line segment (1) A straight path joining two points, called endpoints of the line segment. A line segment can be any length and is the shortest path between two points.

logic grid (4) A grid of rows and columns used to organize the information in a problem.

longitude (4) A measure (in degrees) of how far east or west of the prime meridian a location is on Earth; determined by semicircles of longitude connecting the North Pole and the South Pole.

ABCDEFGHIJKLMNOPQRSTUVWXYZ

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M

magnitude estimate (4) An estimate of whether a solution is in the tens, hundreds, thousands, or more.

map legend (4) A diagram that explains the symbols, markings, and colors on a map. Also called a map key.

map scale (3) A rate that compares the distance between two locations on a map with the actual distance between them. The rate is often represented by a labeled line segment, similar to a ruler.

mathematics (1) A study of relationships among numbers, shapes, and patterns. Mathematics is used to count and measure things, to discover similarities and differences, to solve problems, and to learn about and organize the world.

mean (average) (3) A typical or middle value for a set of numbers. It is found by adding the numbers in the set and then dividing the total by the number of values in the set.

Example: 2, 4, 5, 9, 10 = 30; 30 ÷ 5 = 6; The mean is 6.

median (3) The middle value in a set of data when the data are listed in order from smallest to largest (or largest to smallest). If there is an even number of data points, the median is the mean of the two middle values.

Example: 2, 3, 4, 6, 10 - the median is 4 because it is the middle value.

memory keys (2) The [M+], [M-], and [MRC] calculator keys. The [M+] key is used to add a number to the number stored in the calculator's memory; the [M-] key is used to subtract a number from the number in memory. The [MRC] key, pressed once, displays the number currently stored in memory; when the key is pressed twice, the calculator's memory is cleared.

meridian bar (4) A device on a globe that shows degrees north and south of the equator.

meter (m) (1) In the metric system, a unit of length equal to 10 decimeters, 100 centimeters, or 1000 millimeters.

metric system (1) A measurement system based on the base-10 numeration system and used in most countries in the world. Units for linear measure (length, distance) include millimeter, centimeter, meter, kilometer; units for mass (weight) include gram and kilogram; units for capacity (amount of liquid or other pourable substance a container can hold) include milliliter and liter.

middle value (1) The number in the middle when a set of data is organized in sequential order; also the median.

millimeter (mm) (3) In the metric system, a unit of length equal to 1/10 of a centimeter or 1/1000 of a meter.

mixed number (4) A number that has a whole number part and a fraction part.

Example: 2 is equal to 2 + .

mode (2) The value or category that occurs most often in a set of data.

multiples (1) Multiples of numbers are the product of that number and whole numbers.

Example: 45 is a multiple of 5 because 45 = 5 x 9.

multiplication (2) An operation used to find the total number of things in several equal groups. Numbers being multiplied are called factors. The result of multiplication is called the product. In 5 x 12 = 60, 5 and 12 are factors. 60 is the product. Division "undoes" multiplication: = 12 and = 5.

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N

name-collection box (1) A box-like diagram containing a number, used for collecting equivalent names for that number.

negative number (1) A number less than (below) 0.

net score (4) The final score of a turn or game after any operations have been done.

Example: In the game of Factor Captor, your first move is 29, your opponent's move is 1. You get your net score, 28, by subtracting 1 from 29.

net weight (3) The weight of the contents of a container without including the weight of the container.

nonagon (3) A nine-sided polygon.

number line (1) A line on which points correspond to numbers.

number model (1) A number sentence that shows how the parts of a number story are related.

Example: 5 + 8 = 13; 27 - 11 = 16; 3 x 30 = 90; = 7.

number sentence (1) A sentence that is made up of numerals and a relation symbol (=, <, >). Most number sentences also contain at least one operation symbol (+, -, x, ÷).

number story (K) Story problems; word problems that put numbers and number relationships into a real world context.

numerator (1) The top number in a fraction. The number of equal parts being considered when a whole is divided into equal parts. In the fraction, a is the numerator.

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O

obtuse angle (4) An angle greater than 90 degrees and less than 180 degrees.

octagon (1) An eight-sided polygon.

odd number (2) A whole number that is not evenly divided by 2, such as 1, 3, 5, and so on. When an odd number is divided by 2, the remainder is 1.

opposite of a number (4) A number that is the same distance from zero on the number line as the given number, but on the opposite side of zero.

ordered pair (3) Two numbers in a specific order used to locate a point on a coordinate grid. They are usually written inside parentheses: (2,3). The horizontal coordinate x is given first; the vertical coordinate y is given second.

ordinal number (1) A number used to express position or order in a series, such as first, third, tenth.

origin (1) The point where the x-axis and y-axis intersect on a coordinate grid.

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P

parallel lines (segments, rays) (1) Lines (segments, rays) that are the same distance apart, no matter how far extended, and that never meet.

parallelogram (1) A quadrilateral that has two pairs of parallel sides and opposite sides of equal lengths.

pattern (K) An arrangement of objects so one can predict what will come next if the arrangement is continued, such as head, toe, head, toe,________ or blue, red, red, blue, red,________.

pentagon (1) A 5-sided polygon.

percent (%) (2) Per hundred, or out of a hundred. 1% means or 0.01; 15% means or 0.15.

Example: “48% of the students in the school are boys" means that out of every 100 students in the school, 48 are boys.

perfect number (4) A number in which the sum of all its proper factors is equal to the number itself.

Example: 6 is a perfect number because when you add its proper factors the answer is equal to 6: 1 + 2 + 3 = 6.

perimeter (2) The distance around a two-dimensional shape.

perpendicular (4) Two rays, lines, or line segments that form right angles are said to be perpendicular to each other.

pie (circle) graph (3) A graph that uses a circle divided into parts to show the parts of a set of data. The circle represents the whole set of data.

place value (1) The value of a digit in a number is determined by its position. Each place has a value ten times that of the place to its right and one-tenth the value of the place to its left.

plane (3) A flat surface that extends forever.

point (1) An exact location in space. A point has no size. Points are usually shown as a dot labeled by a capital letter.

polygon (1) A closed two-dimensional figure consisting of line segments (sides) connected endpoint to endpoint.

polyhedra dice (1) A three-dimensional solid with varying numbers of faces (i.e., 4, 6, 10, 20). Used in Everyday Mathematics to generate numbers for games.

polyhedron (1) A 3-dimensional shape, whose surfaces (faces) are all flat. Each face consists of a polygon and the interior of the polygon.

pound (lb.) (1) In the U.S. customary system, a unit of weight that is equivalent to 16 ounces.

power (3) A product of factors that are all the same. 5 x 5 x 5 (or 125) is called 5 to the third power, or the third power of 5, because 5 is a factor three times. 5 x 5 x 5 can also be written as 5³.

powers of 10 (4) Written in exponential notation, the exponent shows how many times 10 is a factor.

Example: 100 is equal to 10 x 10 or 10² (exponential notation). 100 is called ten squared, the second power of 10, or 10 to the second power.

precision (of a scale) (3) Accuracy. The smaller the unit, or fraction of a unit used, the more precise the scale.

prime factorization (4) The longest factor string for a number. It is made up of prime numbers only.

Example: The prime factorization of 24 is 2 x 2 x 2 x 3.

prime number (3) A whole number greater than 1 that has exactly two whole-number factors, 1 and itself. A prime number is only divisible by 1 and itself. The first five prime numbers are 2, 3, 5, 7, and 11. See also composite number.

Example: 7 is a prime number because its only factors are 1 and 7

prism (K) A polyhedron with two parallel faces (called bases) that are the same size and shape. Prisms are classified according to the shape of the two parallel bases. The faces (sides) of a prism are always parallelograms, and often rectangles.

probability A number from 0 to 1 that indicates the likelihood that something (an event) will happen. The closer a probability is to 1, the more likely it is that an event will happen. An event with a probability of 0 is impossible. An event with a probability of 1 is a certainty.

product (2) The result of doing multiplication. In the number model "4 x 3 = 12," 12 is the product.

proper factor (4) All the factors of a number except the number itself.

Example: The factors for the number 10 are 1, 2, 5 and 10. The proper
factors are 1, 2, and 5.

protractor (4) A device for measuring or drawing angles. The vertex of the angle should be at the center of the protractor and one side of the angle along the base line of the protractor.

pyramid (1) A polyhedron in which one face (the base) is a polygon and the other faces are formed by triangles with a common vertex (the apex). A pyramid is classified according to the shape of its base.

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Q

quadrangle or quadrilateral (1) A polygon with four sides.

quadruple (2) Four times an amount.

quotient (2) The result after dividing one number by another number; the number of equal shares. In the division number model "11 ÷ 5 = 2 r1," 2 is the quotient.

quadrillion (4) A digit(s) followed by 15 whole-number places. Quadrillion written in number form is 1,000,000,000,000,000 or in exponential form 10¹⁵.

R

radius (4) A line segment from the center of a circle (or sphere) to any point on the circle (or sphere); also, the length of such a line segment.

random number (3) A number that has the same chance of appearing as any other number.

range (1) The difference between the maximum and the minimum in a set of data.

rate (3) A comparison of two quantities with unlike units.

Example: A speed such as 55 miles per hour compares distance with time.

rational number (4) Any number that can be represented in form , where a and b are integers and b is not 0.

ray (3) A straight path that extends infinitely from a point, called its endpoint. A ray is named by its endpoint and another point on the ray.

rectangle (1) A parallelogram with four right angles.

rectangular prism (1) A prism whose faces are all rectangles.

rectangular pyramid (1) A pyramid, the base of which is a rectangle.

reflection (4) "Flipping" a picture or object so that its image is the mirror opposite of the original.

reflex angle (4) An angle whose measure is between 180° and 360°.

regular polygon (1) A convex polygon in which all sides are the same length and all angles are the same size.

regular polyhedron (1) A polyhedron with all faces the same shape and same size. There are five regular polyhedrons:

tetrahedron: 4 faces, each formed by an equilateral triangle
cube: 6 faces, each formed by a square.
octahedron: 8 faces, each formed by an equilateral triangle.
dodecahedron: 12 faces, each formed by a regular pentagon
icosahedron: 20 faces, each formed by an equilateral triangle.

remainder (2) The amount left over when things are divided into equal shares. In the division number model "16 ÷ 3 = 5 r1" the remainder is 1.

rhombus (K) A parallelogram whose sides are all the same length.

right triangle (1) A triangle that has a 90° (right) angle.

rotation (3) A turn around a center point or axis.

rote counting (K) Reciting numbers in order from memory.

rounding (1) Replacing a number with a nearby number that is easier to work with or better reflects the precision of the data.

Example: 12,964 rounded to the nearest thousand is 13,000.

row (1) A horizontal arrangement of objects or numbers in an array or table.

ABCDEFGHIJKLMNOPQRSTUVWXYZ

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S

scale drawing (4) An accurate picture of an object in which all parts are drawn to the same scale. If an actual object measured 33 yards by 22 yards, a scale drawing of it might measure 33 millimeters by 22 millimeters.

scale factor (3) A number that names "how many times as many?" or "what fraction of?" one quantity is of another quantity.

scalene triangle (4) A triangle in which no sides are the same length.

scientific notation (4) A system for representing numbers in which a number is written as the product of a power of 10 and a number that is at least 1 but less than 10. Scientific notation allows writing big and small numbers with only a few symbols.

Example: 4,000,000 in scientific notation is 4 x 10⁶.
0.00001 in scientific notation is 1 x 10^-6

scroll (1) A roll of paper with words and/or pictures written on it.

semicircle (2) Half of a circle; either of two parts of a circle between (and including) the endpoints of a diameter.

significant figures (4) In a count or measurement, digits that reflect the precision of the result: How reliable is the result? How much variation might there be if the count or measurement were repeated? How closely can the measuring instrument measure the object? Significant figures are usually non-zero digits, or 0 when it is between non-zero digits. The distance from the Earth to the Sun is 93,000,000 miles, with two significant digits.

similar figures (3) Figures that have the same shape but are not necessarily the same size.

skip counting (K) Counting by a specified added amount from a specified starting number For example, skip counting by 2’s from 2, would be 2, 4, 6, 8. . . Skip counting by 10’s from 23 would be 23, 33, 43, 53. . .

sphere (1) The set of all points in space that are a given distance (the radius of the sphere) from a given point (the center of the sphere). A ball is shaped like a sphere, as is the Earth. A hemisphere is "half of a sphere;" that is, either of the two parts into which the sphere is divided by its equator (or by any circle on the sphere with its center at the center of the sphere).

square array (4) A rectangular array with the same number of rows as columns.

square number (2) A number that is the product of a whole number multiplied by itself; a whole number to the second power. 25 is a square number, because 25 = 5 x 5. A square number can be represented by a square array.

Example: 35² = 35 x 35 = 1225.

square pyramid (4) A geometric solid consisting of a square base and triangular faces that meet at an apex (point).

square root of a number (4) The square root of a number n is a number which, when multiplied by itself, results in the number n.

Example: 4 is a square root of 16, because 4 x 4 = 16.
The other square root of 16 is -4 because - 4 x (-4) = 16.

square unit (2) A unit used in area measurement.

standard notation (4) The most familiar way of representing whole numbers, integers, and decimals by writing digits in specified places.

standard unit (1) A uniform unit of measure.

subtraction (1) A mathematical operation based on "taking away" or comparing. The number being subtracted is called the subtrahend; the number it is subtracted from is called the minuend; the result of subtraction is called the difference. In 45 - 12 = 33, 45 is the minuend, 12 is the subtrahend, and 33 is the difference. Addition "undoes" subtraction. 45 - 12 = 33 and 45 = 12 + 33.

sum (1) The result of adding two or more numbers.

symmetry (1) A figure that when divided into two parts has each part the exact mirror image of the other part.

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T

tally mark (K) Marks used to keep track of data (|||| |||).

tangent (4) Intersecting at exactly one point.

template (1) A pattern used as a guide in making something accurately.

tessellation (4) An arrangement of closed shapes that covers a surface completely without overlaps or gaps.

tetrahedron (2) A polyhedron with four faces.

three dimensional (3-D) (1) Objects with thickness as well as length and width.

tiling (3) Covering a surface with uniform shapes so there are no gaps or overlaps, except possibly gaps around the edges.

translation (slide) (4) The motion of an object or picture along a straight line.

transparent mirror (4) A mirror with a front and back face that has a recessed edge used for drawing lines of symmetry.