Definition
Expression
An expression is a mathematical phrase that represents a value without making an equality claim.
What it means
An expression is something you can read as a calculation or value. In 4a − 3, the letter a can change, so the expression’s value can change. You can evaluate it when a value is given, or simplify it, without turning it into a statement to solve.
Remember it
Expression: a value to work out. Equation: two expressions compared with “=”.
Example
For the expression 4a − 3, let a = 5. Substitute 5: 4 × 5 − 3 = 17. The expression has value 17.
Watch for
4a − 3 = 17 is an equation, because the equals sign makes a claim about two values.
Common mix-up
An expression can contain several terms, but it is not automatically an equation.
Exact meaning
A mathematical expression is a combination of numbers, variables, operation symbols, and grouping symbols that represents a value or quantity. By itself, it does not assert that two expressions are equal or compare them.