refilling vs replacement

refilling and replacement both are nouns.

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

As nouns, refilling and replacement are synonyms defined as:

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

Other synonyms of refilling include renewal, replenishment.

refilling (noun)	replacement (noun)
filling again by supplying what has been used up	the act of furnishing an equivalent person or thing in the place of another
	a person or thing that takes or can take the place of another
	an event in which one thing is substituted for another
	a person who follows next in order
	someone who takes the place of another person
	filling again by supplying what has been used up