# Level 3-4 Algebra - Expressions

You'll have come across expressions in your KS3 Maths lessons. By now you'll know that expressions are a very important part of algebra and, for that matter, of maths in general.

Algebra is all about using symbols, usually letters, to represent a number that we don’t yet know. We call these letters *variables*, as their value can change, or vary, depending on the situation. A situation can be written down as a mathematical sentence, or *an expression*. So, in Algebra, you can think of an expression as one or a number of mathematical symbols that represent a number or quantity. Expressions can contain any number of numbers, letters and symbols. Even a single number on its own is an expression.

As with any test, take your time, read each question carefully and think about your answer. Think you've mastered expressions? Then see how well you can express yourself by playing this quiz!