hypotonus vs tonicity

hypotonus and tonicity both are nouns.

Word	Noun	Adjective	Verb	Adverb
hypotonus	Yes	No	No	No
tonicity	Yes	No	No	No

As nouns, tonicity is a hypernym of hypotonus; that is, tonicity is a word with a broader meaning than hypotonus:

hypotonus: (of muscular tissue) the state of being hypotonic
tonicity: the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli

Other hypernyms of hypotonus include tone, tonus.

hypotonus (noun)	tonicity (noun)
(of muscular tissue) the state of being hypotonic	the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli