replacement vs fluctuation

replacement and fluctuation both are nouns.

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

As nouns, fluctuation is a hypernym of replacement; that is, fluctuation is a word with a broader meaning than replacement:

Other hypernyms of replacement include variation.

replacement (noun)	fluctuation (noun)
the act of furnishing an equivalent person or thing in the place of another	the quality of being unsteady and subject to changes
a person or thing that takes or can take the place of another	an instance of change; the rate or magnitude of change
an event in which one thing is substituted for another	a wave motion
a person who follows next in order
someone who takes the place of another person
filling again by supplying what has been used up