mastication vs gumming

mastication and gumming both are nouns.

Word	Noun	Adjective	Verb	Adverb
mastication	Yes	No	No	No
gumming	Yes	No	No	No

As nouns, gumming is a hyponym of mastication; that is, gumming is a word with a more specific, narrower meaning than mastication:

mastication: biting and grinding food in your mouth so it becomes soft enough to swallow
gumming: ineffectual chewing (as if without teeth)

Other hyponyms of mastication include chomping, mumbling, rumination.

mastication (noun)	gumming (noun)
biting and grinding food in your mouth so it becomes soft enough to swallow	ineffectual chewing (as if without teeth)