with sides of length 1 Unit fraction, a reciprocal of a positive integer Unit imaginary number, square root of negative 1 Unit impulse, an impulse of height 1 Unit interval, an interval of distance 1 Unit matrix, a diagonal matrix such that all elements on the main diagonal are 1 and all the others are zero Unit number, the number 1 Unit round-off, an upper bound on the relative error due to rounding in floating point Unit set, a singleton, a set with exactly 1 element Unit sphere, a sphere with a radius of length 1 Unit square, a square with sides of length 1 Unit vector, a vector with length equal to 1 Military Active service unit, the former Provisional Irish Republican Army cell Military unit, an homogeneous military organization whose administrative and command functions are self-contained Sayeret Matkal (The Unit), the Israeli special forces unit Other uses Unit (Cristian Fleming) (born 1974), electronic musician based in New York City Unit (housing), a self-contained suite of rooms within a set of similar dwellings Unit (Norway), a government directorate Unit, course credit at a school or other educational institution Multiple unit, self-propelled train carriage capable of coupling other units of the same type See also Unit testing, a method by which individual units of source code are tested Head unit, a component of a stereo system mounted inside of a vehicle Air unit (disambiguation) Piece (disambiguation) Subunit (disambiguation) UNITA, the second-largest political party in Angola Unite (disambiguation) Unity (disambiguation) United (disambiguation)