SET' The TERM 'SET' is a four-letter word that can be used to describe the duration of something. It is often used to refer to a period of time that has been predetermined or established, such as the length of a meeting, the amount of time a task should take, or the amount of time a project should last. The TERM can also be used to refer to the amount of time something is expected to last, such as a job, a relationship, or a vacation.