syntony vs mental state

syntony and mental state both are nouns.

Word	Noun	Adjective	Verb	Adverb
syntony	Yes	No	No	No
mental state	Yes	No	No	No

As nouns, mental state is a hypernym of syntony; that is, mental state is a word with a broader meaning than syntony:

syntony: the state of being normally responsive to and in harmony with the environment.
mental state: (psychology) a mental condition in which the qualities of a state are relatively constant even though the state itself may be dynamic

Other hypernyms of syntony include mental condition, psychological condition, psychological state.

syntony (noun)	mental state (noun)
the state of being normally responsive to and in harmony with the environment.	(psychology) a mental condition in which the qualities of a state are relatively constant even though the state itself may be dynamic