tonic vs tonus

tonic and tonus both are nouns.

Word	Noun	Adjective	Verb	Adverb
tonic	Yes	Yes	No	No
tonus	Yes	No	No	No

tonic (noun)	tonus (noun)
a medicine that strengthens and invigorates	the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli
(music) the first note of a diatonic scale
a sweet drink containing carbonated water and flavoring
lime- or lemon-flavored carbonated water containing quinine

tonic (adjective)	tonus (adjective)
(used of syllables) bearing the principle stress, usually accompanied by a change in pitch
employing variations in pitch to distinguish meanings of otherwise similar words
of or relating to or producing normal tone or tonus in muscles or tissue
imparting vitality and energy
relating to or being the keynote of a major or minor scale