An expression is a mathematical phrase. It contains numbers, variables, and operations, but no equals sign. 3x + 5, 2(a + b), and x² − 4 are expressions. An equation, by contrast, states that two expressions are equal.

Expressions can be simplified, evaluated, or factored. Simplifying means combining like terms: 3x + 2x becomes 5x. Evaluating means substituting values for variables: if x = 2, then 3x + 5 = 11. Factoring rewrites an expression as a product: x² − 4 = (x − 2)(x + 2).

Expressions are the building blocks of algebra. They appear in formulas, functions, and equations. Learning to manipulate them is a core skill. The rules are consistent, but fluency takes practice. Once mastered, expressions become a flexible language for describing relationships.

• Combination of numbers, variables, and operations
• No equals sign
• Can be simplified, evaluated, or factored
• Building blocks of algebra