A sequence is a word meaning "a set of related events, movements or items that follow each other in a particular order".

It is used in mathematics and other disciplines. In ordinary use, it means a series of events, one following another. In maths, a sequence is made up of several things put together, one after the other. The order that the things are in matters. For example, both (Blue, Red, Yellow) and (Yellow, Blue, Red) are sequences, but they are not the same. Sequences made up of numbers are also called progressions.