tonus vs tenseness

tonus and tenseness both are nouns.

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

As nouns, tenseness is a hypernym of tonus; that is, tenseness is a word with a broader meaning than tonus:

tonus: the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli
tenseness: the physical condition of being stretched or strained

Other hypernyms of tonus include tautness, tension, tensity.

tonus (noun)	tenseness (noun)
the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli	the physical condition of being stretched or strained
	(psychology) a state of mental or emotional strain or suspense