Octave

Octave (Lat. octavus, 'eighth'), in the church calendar, is the eighth day after a festival, counting in the festival day itself; also, the week after a church festival.—In Music octave is the interval between any musical note and its most perfect concord, which is double its pitch, and occupies the position of the eighth note from it on the diatonic scale. The name octave is often given to the eighth note itself as well as to the interval.