One of the standard Western musical modes. The name was not used by the ancient Greeks, and was first employed by Glareanus in Dodecachordon (1547).
In ecclesiastical and modern usage, the rarely-used locrian mode is the diatonic octave-species from B to B, in ascending order thus ("t" = whole-tone, "s" = semitone):
B C D E F G A B s t t s t t t