What is an expression?

An expression is defined as a mathematical sentence that consists of constants (which are fixed values, like numbers) and variables (which can represent unknown values, often denoted by letters like x or y). Expressions can include operations such as addition, subtraction, multiplication, and division but do not include an equality sign. This means they do not assert that two things are equivalent, unlike equations.

For example, the expression 3x + 5 is a combination of the constant 5 and the variable x, multiplied by 3, showcasing how constants and variables work together in mathematics. Understanding this concept is crucial as it forms the foundation of algebra and helps solve equations and other mathematical problems.