| constant | A symbol that represents a quantity that cannot change. It can be a number, letter or a symbol. |
| equation | A mathematical statement that two expressions are equal. |
| expression | A mathematical phrase that can contain a combination of numbers, variables, or operations. |
| like terms | Terms that contain the same variables raised to the same powers. For example, 3x and −8x are like terms, as are 8xy2 and 0.5xy2. |