decay vs gnaw

decay is a noun but gnaw is not a noun.

Word	Noun	Adjective	Verb	Adverb
decay	Yes	No	Yes	No
gnaw	No	No	Yes	No

As verbs, gnaw is a hyponym of decay; that is, gnaw is a word with a more specific, narrower meaning than decay:

decay (noun)	gnaw (noun)
the organic phenomenon of rotting
a gradual decrease; as of stored charge or current
the process of gradually becoming inferior
the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation
an inferior state resulting from the process of decaying

decay (verb)	gnaw (verb)
fall into decay or ruin	become ground down or deteriorate
lose a stored charge, magnetic flux, or current	bite or chew on with the teeth
undergo decay or decomposition