NLN NEX Math key terms

The top number in a fraction. It tells how many equal parts of the whole are being counted or described, while the bottom number tells how many parts make up one whole.

The bottom number in a fraction. It shows the total number of equal-sized parts the whole has been split into, such as 8 in the fraction 3/8.

Fractions that name the same amount even though their numbers differ, such as 1/2 and 4/8. Multiplying or dividing the top and bottom by the same number creates them.

The smallest number that can serve as the bottom number for two or more fractions at once. Finding it lets you add or subtract fractions with unlike denominators.

The fraction you get by flipping a fraction upside down, so the top and bottom numbers trade places. A number times its reciprocal always equals 1, which makes reciprocals useful for dividing fractions.

A way of writing a number as a part out of 100. For example, 45% means 45 out of every 100, and it can be rewritten as the decimal 0.45 or the fraction 45/100.

A comparison of two quantities by division, often written with a colon, as a fraction, or with the word 'to'. It tells how much of one thing there is compared with another.

A statement that two ratios are equal, such as 3/4 = 9/12. Proportions are solved by cross-multiplying to find an unknown quantity in a comparison.

A rate expressed as an amount per single unit of another quantity, such as miles per one hour or dollars per one pound. It is found by dividing the two quantities involved.

The largest whole number that divides evenly into every number in a group. It is used to simplify fractions down to lowest terms.

The smallest number, other than zero, that is a multiple of each number in a group. For 4 and 6 the least common multiple is 12, which helps when working with fractions.

The agreed sequence for evaluating a math expression: work through grouping symbols, then powers, then multiplication and division left to right, then addition and subtraction left to right.

Any whole number, whether positive, negative, or zero, with no fractional or decimal part. Examples include -12, 0, and 7, but not 2.5 or 1/3.

A number's distance from zero on the number line, written with vertical bars. Because distance is never negative, the absolute value of both -6 and 6 is 6.

A letter or symbol that stands for an unknown amount or a value that can change. In the equation 5x + 2 = 17, the letter x is the variable.

A mathematical phrase built from numbers, variables, and operation signs, with no equals sign. For example, 4n - 7 becomes a specific value once you know what n is.

The number that is multiplied by a variable in a term. In 9y, the coefficient is 9; when no number is written, as in y, the coefficient is understood to be 1.

A number in an expression or equation that stands alone, not attached to any variable. In 3x + 8, the constant term is 8 because its value never changes.

Terms that have exactly the same variable parts, such as 5m and 11m. Only like terms can be combined by adding or subtracting their coefficients into a single term.

An equation in which the variable appears only to the first power, so its graph is a straight line. Solving one means finding the single value that makes the two sides equal.

A rule letting you multiply a value outside parentheses by each term inside them. It says that a times the sum of b and c equals a times b plus a times c.

The operation that undoes another one: addition undoes subtraction, and multiplication undoes division. Solving an equation means applying inverse operations to isolate the variable.

A math sentence comparing two quantities that are not necessarily equal, using symbols such as less than, greater than, or at most. Its solution is a whole range of values rather than a single number.

All the values of the variable that make an equation or inequality true. A linear equation usually has one member, while an inequality typically has endlessly many, often shown on a number line.

A measure of how steep a line is, found by dividing the vertical change between two points by the horizontal change. A positive slope rises, a negative slope falls, and a flat line has slope zero.

The point where a line crosses the vertical axis of a graph, written as the y-value when x equals zero. It often represents a starting amount in real-world problems.

The total distance around the outside edge of a flat shape. It is found by adding the lengths of all the sides, and the answer is given in linear units such as inches or meters.

The amount of flat surface covered by a two-dimensional shape, measured in square units such as square feet. Rectangles are measured by multiplying length by width.

The distance all the way around a circle, the circular version of perimeter. It equals pi multiplied by the circle's 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 the diameter and is needed to compute circumference and the area of a circle.

The full width of a circle measured straight across through its center, from one edge to the opposite edge. It equals twice the radius and is used in circumference formulas.

The amount of three-dimensional space a solid occupies, measured in cubic units such as cubic centimeters. A rectangular box's volume is length times width times height.

Changing a measurement from one unit to another without changing the actual amount, such as turning 3 feet into 36 inches. You multiply or divide using the relationship between the units.

The number you multiply every length by when enlarging or shrinking a figure. A scale factor of 2 doubles each side, while a factor of 0.5 cuts each side in half.

The average of a data set, found by adding all the values and dividing by how many values there are. It is pulled upward or downward by unusually large or small numbers.

The middle value in a data set when the numbers are arranged in order. If there is an even count, the median is the mean of the two middle values.

The value that appears most often in a data set. A set can have no mode, one mode, or several modes if multiple values tie for the highest frequency.

The spread of a data set, calculated by subtracting the smallest value from the largest value. It gives a quick sense of how widely the numbers vary.

A data value that sits far away from the rest of the values in a set. Outliers can strongly shift the mean while barely affecting the median.