refilling vs replenishment

refilling and replenishment both are nouns.

Word	Noun	Adjective	Verb	Adverb
refilling	Yes	No	No	No
replenishment	Yes	No	No	No

As nouns, refilling and replenishment are synonyms defined as:

refilling and replenishment: filling again by supplying what has been used up

Other synonyms of refilling include renewal, replacement.

refilling (noun)	replenishment (noun)
filling again by supplying what has been used up	filling again by supplying what has been used up