An academic term' or term is a division of an academic year, the time during which an educational institution holds classes. The schedules adopted vary widely.

In most countries, the academic year begins with the start of autumn and ends during the following summer. In Southern Hemisphere countries, this means that the academic year lasts from February or March to November or December; in Northern Hemisphere countries, it lasts from August or September to May, June or July instead. The summer may or may not be part of the term system.

A 'semester' (from the Latin meaning "six-monthly") has come to mean either of two academic terms, generally excluding the summer or January terms, if any, and so is about 16 to 18 weeks long. The word 'semester' is sometimes used as a synonym for a 'term', as in a 'summer semester'.

A 'trimester' (from the Latin meaning "three-monthly") divides the academic year into three periods. At the University of Michigan, for example, the Fall trimester (informally still called 'semester') operates from September through December; the Winter trimester runs from January through April; and the Spring-Summer trimester operates from May through August, as two half-trimesters. Most Spring-Summer classes either meet double-time for 7 – 8 weeks in May and June or double-time/double-plus-time for 6 – 8 weeks in July and August (with summer half-term classes sometimes starting in the last week of June). In some jurisdictions,^[specify] "trimester" is used in its original meaning to indicate a quarter system (since three months is exactly a quarter of a year), or a variation of it.