**1.1 Variables and Expressions**

**Definitions:**

**Variables**are letters or symbols used in place of a quantity we don’t know yet.**An Expression**is a mathematical phrase that contains numbers, variables and symbols.**Symbols or Operators**are signs such as (+) and (-). Numbers and variables have operators.**Coefficient**is the number attached to a variable such as 7d. You have to multiply the number 7 by the variable d.**A Constant**is the number that stays fixed in an expression. For example: 4x + 10. The constant is 10.**Terms**are parts of the expression. For example: In the expression 2x + 3, there are two terms.