unison vs coincidence

unison and coincidence both are nouns.

Word	Noun	Adjective	Verb	Adverb
unison	Yes	No	No	No
coincidence	Yes	No	No	No

As nouns, coincidence is a hypernym of unison; that is, coincidence is a word with a broader meaning than unison:

Other hypernyms of unison include co-occurrence, concurrence, conjunction.

unison (noun)	coincidence (noun)
(music) two or more sounds or tones at the same pitch or in octaves	the temporal property of two things happening at the same time
occurring together or simultaneously	the quality of occupying the same position or area in space
corresponding exactly	an event that might have been arranged although it was really accidental