HiSET Math key terms

A whole number that can be positive, negative, or zero, with no fractional or decimal part. Examples include -7, 0, and 12, but not 3.5.

Any number that can be written as a fraction of two integers, with a nonzero denominator. This includes terminating and repeating decimals, integers, and simple fractions.

The distance a number sits from zero on the number line, always written as a nonnegative value. The absolute value of both -6 and 6 is 6.

A straight line marked with evenly spaced points representing numbers, increasing left to right. It is used to compare values, show negatives, and picture distances.

A way of writing part of a whole as one number over another, such as 3/4. The bottom number names how many equal parts exist and the top names how many are taken.

The number you multiply by to get a product of 1, found by flipping a fraction upside down. The reciprocal of 5/8 is 8/5, and it is used when dividing fractions.

A ratio that compares a number to 100, written with a percent sign. For example, 45% means 45 out of every 100, or 45/100, which equals 0.45.

The amount a value grows, expressed as a percent of the original value. It is found by dividing the change by the starting amount and multiplying by 100.

A comparison of two quantities by division, often written with a colon such as 3:5. It tells how much of one thing there is for each unit of another.

An equation stating that two ratios are equal, such as 2/3 = 8/12. Solving one usually means finding a missing value by cross-multiplying.

A rate in which the second quantity is exactly one unit, like 55 miles per 1 hour. It makes comparing costs or speeds easy because everything is measured per single unit.

The agreed sequence for evaluating expressions: parentheses first, then exponents, then multiplication and division left to right, then addition and subtraction left to right.

A small raised number showing how many times a base is multiplied by itself. In 4^3, the exponent 3 means 4 x 4 x 4, which equals 64.

A number that, when multiplied by itself, gives the original value. The square root of 49 is 7 because 7 x 7 equals 49.

A compact way to write very large or very small numbers as a value between 1 and 10 multiplied by a power of ten, such as 3.2 x 10^5.

The total distance around the outside edge of a flat shape. For a rectangle it equals twice the length plus twice the width.

The amount of flat surface a shape covers, measured in square units. A rectangle's area equals its length multiplied by its width.

The amount of space a three-dimensional object fills, measured in cubic units. For a rectangular box, it equals length times width times height.

The distance all the way around a circle. It equals pi times the diameter, or about 3.14 times the diameter.

The distance from the center of a circle to any point on its edge. It is exactly half of the diameter.

The distance straight across a circle through its center point. It equals twice the radius and is used to find circumference and area.

A triangle containing one 90-degree angle. Its longest side, opposite the right angle, is called the hypotenuse.

The longest side of a right triangle, located directly across from the 90-degree angle. Its length can be found using the Pythagorean theorem.

A rule for right triangles stating that the squares of the two shorter sides add up to the square of the hypotenuse, written a^2 + b^2 = c^2.

Shapes with the same angles whose matching sides are in equal proportion, though the sizes may differ. One is a scaled copy of the other.

The number you multiply each side of a figure by to produce a similar figure. A scale factor of 2 doubles every length in the original shape.

Changing a measurement from one unit to another, such as inches to feet, by multiplying by a conversion ratio. Careful setup keeps the unwanted units canceling out.

The average of a data set, found by adding all values and dividing by how many values there are. It is affected strongly by unusually large or small values.

The middle value of a data set when the numbers are arranged in order. If there are two middle values, the median is their average.

The value that appears most often in a data set. A set can have one mode, several modes, or no mode at all if every value appears equally often.

The difference between the largest and smallest values in a data set. It gives a quick sense of how spread out the data are.

A data value that is far away from the rest of the group. Outliers can pull the mean noticeably while leaving the median nearly unchanged.

A number from 0 to 1 describing how likely an event is, where 0 means impossible and 1 means certain. It can be written as a fraction, decimal, or percent.

Two events where the outcome of one does not change the chance of the other. For such events, you multiply their individual probabilities to find the chance both happen.

The complete list of all possible outcomes of a probability experiment. For one coin flip, the sample space is heads and tails.

A letter or symbol standing in for an unknown or changing number in an expression or equation. In 3x + 5, the letter x is the variable.

A mathematical phrase combining numbers, variables, and operations without an equals sign, such as 4y - 9. It can be simplified or evaluated but not solved.

A statement that two mathematical expressions are equal, joined by an equals sign. Solving it means finding the value of the variable that makes the statement true.

An equation in which each variable appears to the first power only, producing a straight line when graphed. An example is y = 2x + 1.

A measure of how steep a line is, found as the rise divided by the run between two points. A positive slope rises left to right; a negative slope falls.

The point where a graphed line crosses the vertical axis, occurring where x equals zero. In y = 3x + 7, the y-intercept is 7.

A statement comparing two expressions that are not necessarily equal, using symbols like <, >, or >=. Its solution is a range of values rather than a single number.

A rule that assigns exactly one output value to each input value. Each input has a single result, so a graph of a function passes the vertical line test.