mastication vs mumbling

mastication and mumbling both are nouns.

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

As nouns, mumbling is a hyponym of mastication; that is, mumbling 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
mumbling: ineffectual chewing (as if without teeth)

Other hyponyms of mastication include chomping, gumming, rumination.

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