A cadet is a trainee. The term is frequently used to refer those training to become an officer in the military, often a person who is a junior trainee. Its meaning may vary between countries. The term is also used in civilian contexts and as a general attributive, for example in its original sense of a branch of a ruling house which is not currently in the direct line of succession.

The Harwell CADET was the first fully transistorized computer in Europe, and may have been the first fully transistorized computer in the world.