•  7th Grade Key Terms: Absolute Value The distance of a number from zero on a number line, shown by the symbol Algebraic Expression An expression that contains at least one variable Associative Property of Addition The property that states that for all real numbers a, b, and c, the sum is always the same, regardless of their grouping. Ex. 2+3+8=(2+3)+8=2+(3+8) Associative Property of Multiplication The property that states that for all real numbers a, b, and c, their product is always the same, regardless of their grouping. Ex. 2*3*8=(2*3)*8=2*(3*8) Bisector A line segment, line, or plane that divides a geometric figure into two congruent halves. Box-and-Whisker Plot A graph that displays the highest and lowest quarters of data as whiskers, the middle two quarters of the data as a box, and the median. Commutative Property of Addition The property that states that two or more numbers can be added in any order without changing the sum.  Ex. 8+20=20+8 Commutative Property of Multiplication The property that states that two or more numbers can be multiplied in any order without changing the product.  Ex. 6*12=12*6 Congruent Having the same size and shape. Constant of Proportionality (y=kx) The constant value of the ratio of two proportional quantities x and y; usually written y = kx, where k is the factor of proportionality Corresponding Angles A pair of angles formed by a transversal and two lines. Corresponding Sides Matching sides of two or more polygons. Cross-Section A section formed by a plane cutting through an object, usually at right angles to an axis. Diagonal Connecting two nonadjacent angles or vertices of a polygon or polyhedron, as a straight line. Dilation A dilation is a type of transformation that changes the size of the image. Direct Proportions The relation between quantities whose ratio remains constant, when A changes then B changes by the same factor; also called direct ratio Direct Variation When two variables are related in such a way that the ratio of their values always remains the same. Distributive Property The property that states if you multiply a sum by a number, you will get the same results if you multiply each addend by that number and then add the products.  Ex. 5(20+1)=5*20+5*1 Endpoint A point at the end of a line segment or ray. Histogram A bar graph that shows the frequency of data within equal intervals. Indirect Proportion When A increases, B decreases by the same factor.  Also called Inverse Proportion. Integer The set of whole numbers and their opposites. Inter-quartile Range The difference between the upper and lower quartiles in a box and whisker plot. Intersection 1. The point or set of points where one line, surface, or solid crosses another. 2. The set that contains only those elements shared by two or more sets. Inverse Variation A relationship between two variables in which the product is a constant. When one variable increases the other decreases in proportion so that the product is unchanged. Inversely Proportional When one variable is directly proportional with the multiplicative inverse (reciprocal) of the other, or equivalently if their product is a constant. Line A straight path that extends without end in opposite directions. Line Plot A number line with marks or dots that show frequency. Line Segment A part of a line between two endpoints Linear Equation An equation whose solutions form a straight line on a coordinate plane. Mean The sum of the items in a set of data divided by the number of items in the set.  Also called average. Median The middle number, or the mean (average) of the two middle numbers in an ordered set of data. Mode The number or numbers that occur most frequently in a set of data; when all numbers occur with the same frequency, we say there is no mode. Natural Number The numbers used for counting. That is, the numbers 1, 2, 3, 4, etc. Negative A real quantity having a value less than zero Opposite Two numbers that are an equal distance from zero on a number line, also called additive inverse. Outlier A value much greater or much less than the others in a data set. Parallel Lines Lines in a plane that do not intersect. Perpendicular Lines Lines that intersect to form right angles. Plane A flat surface that extends forever. Point An exact location in space. Polyhedron A three-dimensional figure in which all the surfaces or faces are polygons. Positive Any numbers greater than zero Quartile Three values, one of which is the median, that divide a data set into fourths. Range The difference between the greatest and least values in a data set. Rate A ratio that compares two quantities measured in different units. Ray A part of a line that starts at one endpoint and extends forever. Reflection A transformation of a figure that flips the figure across a line. Rotation A transformation in which a figure is turned around a point. Scale Drawing A drawing that uses a scale to make an object smaller than or larger than the real object. Scatter Plot A graph with points plotted to show a possible relationship between two sets of data. Sign The positivity or negativity of a number, quantity, or expression. any symbol indicating an operation Similar Figures with the same shape but not necessarily the same size. Similarity Two objects with the same shape. Symmetry divides a figure into two mirror-image halves Term The parts of an expression that are added or subtracted.  An element or number in a sequence. Translation A movement (slide) of a figure along a straight line. Variable A symbol used to represent a quantity that can change. Variation The way in which change occurs. Whole Number Whole Numbers are simply the numbers 0, 1, 2, 3, 4, 5, … (and so on)