Six Important Algebra Terms You Must Know for the ACT

By Mark Zegarelli

Algebra is chock-full of words that are useful but often misunderstood. To do well on the ACT Math test, you should be able to define these important terms: variable, constant, equation, expression, term, and coefficient.

  • Variable. A variable is any letter that stands for a number. The most commonly used letters are x and y, but you can use any letter.

  • Constant. A constant is a number without a variable. For example: The equation 6m + 7 = –m has one constant, the number 7.

  • Equation. An equation is any string of numbers and symbols that makes sense and includes an equal sign. For example, here are three equations:


  • Expression. An expression is any string of numbers and symbols that makes sense when placed on one side of an equation. For example, here are four expressions:


  • Term. A term is any part of an expression that’s separated from the other parts by either a plus sign (+) or a minus sign (–). Important: A term always includes the sign that immediately precedes it. For example,

    • The expression 3x – 7 has two terms: 3x and –7.

    • The expression –x2 – 9x + 11 has three terms: –x2, –9x, and 11.

    • The expression


      has one term:


  • Coefficient. A coefficient is the numerical part of a term, including the sign that precedes it (+ or –). Important: Every term has a coefficient. When a term appears to have no coefficient, its coefficient is either 1 or –1, depending on the sign. For example,

    • The term 3x has a coefficient of 3.

    • The term –9x has a coefficient of –9.

    • The term –x2 has a coefficient of –1.

Being clear about the meanings of these six words can help you with any other math you study.