Dictionary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z addition The operation, or process, of calculating the sum of two numbers or quantities (cf Integer Addition and Subtraction Discussion, Fraction Adding and Subtracting Discussion). absolute value The distance a number is from zero on the number line. For example, -5 is 5 units away from zero. It would be written as |-5|. acute angle An angle whose measure is less than 90 degrees (cf Angles Discussion). adjacent angles Two angles that share a ray, thereby being directly next to each other (cf Angles Discussion). affine cipher Affine ciphers use linear functions to scramble the letters of secret messages (cf Cryptography and Ciphers Discussion). alternate exterior angles Angles located outside a set of parallel lines and on opposite sides of the transversal (cf Angles Discussion). alternate interior angles Angles located inside a set of parallel lines and on opposite sides of the transversal (cf Angles Discussion). angle bisector A ray that divides an angle into two congruent angles. area The number of square units needed to cover a surface (cf Length, Area, and Perimeter Lesson). arithmetic mean See mean (cf Mean, Median and Mode Discussion). associative property This property applies both to multiplication and addition and states that you can group several numbers that are being added or multiplied (not both) in any way and yield the same value. In mathematical terms, for all real numbers a, b, and c, (a+b)+c=a+(b+c) or (ab)c=a(bc). average It is better to avoid this sometimes vague term. It usually refers to the (arithmetic) mean, but it can also signify the median, the mode, the geometric mean, and weighted means, among other things (cf Mean, Median and Mode Discussion). average expected payoff An estimate of the amount that will be gained in a game of chance, calculated by multiplying the probability of winning by the number of points won each time (cf Expected Value Discussion). axioms of probability There are three axioms of probability: 1. Probability is always more than zero 2. The chance that something happens is 1,or 100% 3. If two events cannot both occur at the same time, the chance that either one occurs is the sum of the chances that each occurs. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z