GRE Quantitative key terms

A whole number that can be positive, negative, or zero, with no fractional or decimal part, such as -3, 0, or 7.

A number that can be written as a fraction of two integers, where the denominator is not zero; its decimal form either terminates or repeats.

A real number that cannot be written as a fraction of two integers; its decimal form goes on forever without repeating, such as pi or the square root of 2.

An integer greater than 1 whose only positive divisors are 1 and itself, such as 2, 3, 5, and 7; 1 is not prime.

The largest positive integer that divides two or more given integers without leaving a remainder; for 12 and 18, it is 6.

The smallest positive integer that is a multiple of two or more given integers; for 4 and 6, it is 12.

The distance of a number from zero on the number line, always nonnegative; the absolute value of both -5 and 5 is 5.

A comparison of two quantities by division, often written as a to b, a:b, or a/b, showing how many times one value contains the other.

A way of expressing a number as a fraction of 100; for example, 25 percent means 25 out of 100, or one quarter.

A number written above and to the right of a base that tells how many times the base is multiplied by itself; in 2^3, the exponent 3 means 2×2×2.

A letter or symbol, such as x or y, used to represent an unknown number or a quantity that can change in an expression or equation.

An equation whose graph is a straight line and in which each variable appears to the first power only, such as 2x + 3y = 7.

A measure of how steep a line is, equal to its vertical change divided by its horizontal change between two points; often called rise over run.

An equation of the form ax^2 + bx + c = 0, where a is not zero; its graph is a parabola and it can have up to two real solutions.

A mathematical statement comparing two expressions that are not necessarily equal, using symbols such as <, >, ≤, or ≥.

A rule that assigns to each input value exactly one output value; for example, f(x) = x + 2 adds 2 to every input.

A set of two or more linear equations that share the same variables; solving it means finding values that satisfy all equations at once.

An expression made by adding or subtracting terms that each consist of a constant multiplied by variables raised to nonnegative whole-number powers.

The total distance around the outside edge of a flat shape, found by adding the lengths of all its sides.

The amount of flat space inside a two-dimensional shape, measured in square units such as square inches or square meters.

The amount of three-dimensional space a solid object occupies, measured in cubic units such as cubic centimeters, cubic inches, or cubic feet.

A rule for right triangles stating that the square of the hypotenuse equals the sum of the squares of the other two sides: a^2 + b^2 = c^2.

Triangles that have the same shape but not necessarily the same size; their corresponding angles are equal and their corresponding side lengths are proportional.

The distance around the outside of a circle, equal to pi times the diameter or two times pi times the radius.

Two angles whose measures add up to 180 degrees; when placed next to each other, they form a straight line.

The point that divides a line segment into two equal parts; its coordinates are the averages of the endpoints' coordinates.

The arithmetic average of a set of numbers, found by adding all the values and dividing the sum by the number of values.

The middle value in a set of numbers arranged in order; if there is an even number of values, it is the average of the two middle ones.

The value that appears most often in a data set; a set can have one mode, several modes, or no mode if all values occur equally often.

A measure of how spread out numbers in a data set are from their mean; a larger value means the data are more dispersed.

A number between 0 and 1 that expresses how likely an event is, often found by dividing favorable outcomes by total possible outcomes.

An arrangement of items in which order matters; the number of ways to arrange n distinct items is n factorial.

A selection of items in which order does not matter; for example, choosing 3 people from 10 to form a committee.

The difference between the third quartile and the first quartile of a data set; it measures the spread of the middle 50 percent of values.