infantryman vs fusilier

infantryman and fusilier both are nouns.

Word	Noun	Adjective	Verb	Adverb
infantryman	Yes	No	No	No
fusilier	Yes	No	No	No

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

infantryman: fights on foot with small arms
fusilier: (formerly) a British infantryman armed with a light flintlock musket

Other hyponyms of infantryman include grenade thrower, grenadier, doughboy, musketeer.

infantryman (noun)	fusilier (noun)
fights on foot with small arms	(formerly) a British infantryman armed with a light flintlock musket