# Math Glossary: a

 Acute Angle An angle which measures less than 90 degrees. Addition The operation of increasing one number by a certain amount to get a sum. Algebra A branch of mathematics in which variables are substituted for unknown values to solve a particular problem. Angle The measure of the distance between two values that share a common point (measured in degrees). Area The amount of space taken up by a two-dimensional figure. Arithmetic A general area of math dealing with addition, subtraction, multiplication, and division. Associative Property Basic property of math that applies to certain operations and says that the order of the parenthesis does not matter, i.e. (4+5)+3 = 4+(5+3) Abscissa The x-coordinate. In the point (6,3), the abscissa is 6. Absolute Value The distance away from the origin. This means the positive value of a number. For example, the absolute value of -6 is 6. Additive Inverse Two numbers that equal 0 when added together. The numbers 14 and -14 are additive inverses of each other. Adjacent Angles Two angles which share a common side and the same vertex. Altitude The distance from the base of a figure to the highest point in the figure, especially in a triangle. Amplitude Half the distance from the highest point to the lowest point. The amplitude of a normal sine curve is 1, since the distance between top and bottom is 2. Antiderivative A function who\'s derivative is the given function. Given a function like f(x) = 4x, the antiderivative F(x) = 2x^2. Arithmetic Mean The average of a set of numbers. The arithmetic mean of 8 and 4 is (8+4)/2, or 6. Arithmetic Sequence A sequence of numbers formed by adding a common term. The sequence of 4,7,10,13... is arithmetic because it is formed by adding 3 over and over. Axis of Symmetry A line that divides a figure into two perfect mirror images of each other. The diameter of a circle is one of many lines of symmetry.