# MATH Vocab Glossary

In each issue, we cover several different math skills. There are vocabulary words associated with each skill. It's easy to get a few of them mixed up. Here, we'll keep a list of the year's words and their definitions that you can refer to.

**GLOSSARY**

of mathematical vocabulary used in *Scholastic MATH* Magazine during the 2010–11 year through the current issue.

- In parentheses, we list the issue of first mention and the first page of the article containing that vocabulary.
- Vocabulary from the current issue is in bold.

Acute angle: Measures greater than 0º but less than 90º; narrower than a right angle (Jan. 10, p. 14)

Area: The region inside a polygon measured in square units (Jan. 31, p. 12)

Attributes: A property or characteristic of an object, used when looking for patterns (Oct. 18, p. 8)

Average: See mean (Oct. 18, p. 14)

Bar graph: Used to compare different amounts; the heights of the rectangular bars represent the quantities being compared. (Sept. 6, p. 6)

Base: In an exponent expression, the number being used as a factor (Oct. 18, p. 12). In geometry, the bottom of a shape or solid.

Box-and-whisker plot: Graph consisting of a number line, a rectangular “box” and two line-segment “whiskers” which allows you to quickly see where most data in a set falls, and the data’s range (Dec. 13, p. 6)

Circle graph: Used to compare different portions or percents of a whole; the greater the angle measure of each "slice" of the circle, the greater the portion. (Feb. 21, p. 8)

Circumference: The distance around a circle (Mar. 14, p. 6)

Combination: A way of selecting several things out of a larger group, where the order of the things does not matter. (Feb. 21, cover)

Composite: Numbers with more than two factors (Oct. 18, back page)

Coordinate grid: Formed by the intersection of a horizontal number line (the x axis) and a vertical number line (y axis) (Mar. 14, p. 12)

Decimals: Decimal numbers contain a decimal point. The decimal portion of the number are the place values to the right of the decimal point. (Sept. 6, p. 14)

Denominator: Bottom part of a fraction (Dec. 13, p. 8)

Diameter: The distance across a circle through its center; twice the radius (Mar. 14, p. 6)

Double-line graph: Used to compare two sets of data over time (Apr. 11, p. 6)

Equation: A mathematical sentence containing an equals (=) sign (Sept. 6, p. 2)

Estimation: Approximating an amount based on mathematical reasoning (Sept. 6, p. 4)

Exchange rate: What one country’s form of currency is worth in the currency of another country (Jan. 10, p. 12)

Expanded form: Writing out a number in a form that shows the place value of each digit (Sept. 27, p. 14)

Exponent: Tells you how many times to use the base as a factor (Oct. 18, p. 12)

Factors: All the numbers that divide evenly into a number (Sept. 6, p. 10)

Formula: A rule, often expressed as a variable equation, we can use to solve specific problems (Sept. 6, p. 12)

Function: A relationship that pairs each input with exactly one output. Can be represented with ordered pairs, an equation, a mapping diagram, a table, or a graph. (Feb. 21, p. 2)

Geometric progression: A sequence of numbers in which each term is multiplied by the same factor to get the next term (Nov. 8/22, p. 2)

Greatest common factor: The greatest number that is a factor of two or more numbers (Nov. 8/22, back page)

**Hypotenuse: In a right triangle, the side opposite the right angle (May 2, back page)**

Improper fraction: A fraction in which the numerator is greater than the denominator (Dec. 13, p. 12)

Infinity: A quantity without end, often represented by the symbol ∞ (Sept. 27, cover)

Integer: The set of positive and negative natural numbers and zero (...-2, -1, 0, 1, 2...). Negative integers are less than zero, positive integers are greater. (Apr. 11, back page)

**Interest: For a savings account, interest is money earned on the principal (money deposited in the account). (May 2, p. 4)**

**Interest rate: For a savings account, the percent a bank uses to determine how much interest will be earned. (May 2, p. 4)**

Interior angle: An angle formed by two sides of a polygon on the inner side of the polygon. The formula to find the sum of a polygon's interior angles in 180° x (number of sides - 2) (Feb. 21, p. 14)

Inverse operations: Addition and subtraction are inverse operations; so are multiplication and division. To solve for a missing value in an equation, we can "undo" an operation by performing its inverse. (Sept. 6, back page)

Irrational number: The decimal portion of irrational numbers never end or repeat (Jan. 31, p. 8)

Least common multiple (LCM): The lowest number that is a multiple of two numbers (Dec. 13, p. 14)

Line graph: Used to show a change in amounts over time (Sept. 27, p. 8)

Logic line: Problem solving tool, similar to a number line, used to put events in order using a set of clues (Sept. 27, p. 6)

Lowest common denominator (LCD): The least common multiple of the denominators of fractions you are adding or subtracting (Dec. 13, p. 8)

Lowest terms: See simplest form (Dec. 13, cover)

Mean: The sum of the numbers in a set divided by the number of numbers in the set; often called the average (Oct. 18, p. 14)

Median: The middle number when a set of numbers has been ordered from least to greatest; if there are two middle numbers, the median is the average of those two numbers (Dec. 13, p. 6)

Mixed number: Has a whole number part and a fraction part; improper fractions can be rewritten as mixed numbers (Dec. 13, p. 12)

Mode: The number that appears most often in a set (Mar. 14, p. 15)

Multiple: The product of a number and any whole number > 0 (Sept. 6, cover)

Negative exponent: A number to a negative power equals 1 divided by that number to the positive power (Apr. 11, p. 14)

Numerator: Top part of a fraction (Dec. 13, p. 8)

Obtuse angle: Measures greater than 90º but less than 180º; wider than a right angle (Jan. 10, p. 14)

Order of operations: The correct order for performing operations when more than one operation appears in an expression: parentheses, exponents, multiplication and division left to right, addition and subtraction left to right. (Sept. 6, p. 2)

Ordered pairs: Used to locate points on a coordinate grid; written (x, y), it shows how many units to move left or right, and up or down, from the origin (0, 0). (Mar. 14, p. 12)

Percent: A number out of 100; represented by the symbol % (Feb. 21, p. 6)

Percent change: Amount of increase or decrease from an original number to a new number, divided by the original number (Apr. 11, p. 12)

Perfect square: A number for which the square root is an integer (Jan. 31, p. 8)

Perimeter: The distance around a polygon (Jan. 31, p. 12)

Pi: A number approximately equivalent to 3.14 (Mar. 14, p. 6)

Place value: In a number, the value of each digit depends on its position in relation to the other digits: ones place, tens place, hundreds place, etc., or tenths, hundredths, thousandths, etc. (Sept. 6, p. 14)

Powers of 10: When we multiply 10 by itself different numbers of times, the resulting products are powers of 10. Also: 10n, in which n is the number of zeros after the 1. (Sept. 27, p. 12)

Prime factorization: Number expressed as the product pf prime-number factors (Jan. 10, p. 8)

Prime number: A whole number greater than 1 that has only two factors: 1 and itself (Oct. 18, cover)

**Principal: The money you deposit into a savings account (May 2, p. 4)**

**Probability: The chance that an event will occur, expressed as a ratio: outcomes you want to possible outcomes (May 2, p. 14)**

Proportion: Two equivalent ratios (Apr. 11, p. 8)

**Pythagorean theorem: In any right triangle with side lengths a, b, and c (c being the hypotenuse), a ^{2} + b^{2} = c^{2} (May 2, back page)**

Radius: The distance from the center of a circle to any point on the circle (Mar. 14, p. 6)

Range: The difference between the least and greatest values in a set of data (Dec. 13, p. 6)

Rate: Compares measurements of two different types of units, such as distance and time (Sept. 6, p. 12)

Ratio: Compares two different numbers; can be written as a to b, a:b, or Ab (Feb. 21, back page)

Reciprocals: Any two nonzero numbers whose product is 1 (Jan. 10, back page)

Right angle: Measures 90º and looks like the corner of a square (Jan. 10, p. 14)

**Right triangle: A triangle with one right angle (May 2, back page)**

Rounding: The process of replacing a number with an approximately equal but simpler number. Numbers can be rounded up (if the digit to the right of the place value you're rounding to is 5 or greater) or rounded down. (Sept. 6, p. 4)

Simplest form: When a fraction’s numerator and denominator have been divided by their greatest common factor; also known as lowest terms (Dec. 13, back page)

Stacked bar graph: The whole bar represents the total amount and the separate sections represent parts of that total (Jan. 31, p. 6)

Supplementary angles: A pair of angles that add up to 180º; compare to complementary angles (Mar. 14, cover)

Twin primes: Two prime numbers that differ by 2, such as 11 and 13 (Oct. 18, cover)

Unit fraction: A fraction with 1 as the numerator (Nov. 8/22, cover)

Variable: In an expression or equation, a letter used to represent a number (Sept. 27, p. 2)