Terms are the different parts of an expression. A term can be a simple number, a letter, or a combination of a number and letters. For example, `25, 6g, 7h and 17bc` are all terms.

A taxi company charges for fares at a rate of £2.50 plus £1.05 per kilometre. This can be written as an expression:

Fare in `£ = 2.50 + 1.05k`, where `k` is the number of kilometres driven

The 2.50 and 1.05 numbers cannot be added together, because the value of 1.05k changes depending on how many kilometres (k) are driven. The £2.50 and the `1.05k` are different terms.

In an expression `3 + 2x + 7x^2 + 4y`, the `3, 2x, 7x^2` and `4y` are all separate terms. If the letters are different, or have different powers, they are different terms: `x, x^2` and `x^3` are all different terms.

Terms that can be added together are called like terms. Terms that cannot be added together are called unlike terms.

The number 1 is not normally written at the front of a term: so `1x` is written as `x`.