A day fighter is a fighter aircraft equipped only to fight during the day. More specifically, it refers to a multi-purpose aircraft that does not include equipment for fighting at night (such as a radar and specialized avionics), although it is sometimes used to refer to some interceptors as well. The term is an example of a retronym: before the development of effective dedicated night fighter aircraft early in World War II, in effect, all fighter aircraft that were not specifically modified for night combat were day fighters.