(a.) Consisting of seven parts, or having the parts in sets of sevens.

consecutive intervals degree diapason diatessaron diatonic interval diatonic semitone enharmonic diesis enharmonic interval fifth fourth half step halftone heptadic heptagonal heptahedral heptamerous heptangular interval less semitone melodic interval note octave parallel octaves second semitone septempartite septenary septimal septuple sevenfold sixth step third tone unison interval whole step