ETYM Latin nocturnalis, nocturnus, from nox, noctis, night. Related to Night, Nocturn.
1. Of or relating to or occurring in the night.
2. Of or during or relating to the night.
3. (Biology) Belonging to or active during the night.

ETYM French See Nocturn.
A pensive lyrical piece of music (especially for the piano).
In music, a reflective character piece, often for piano, introduced by John Field (1782–1837) and adopted by Chopin.