legionary vs legionnaire

legionary and legionnaire both are nouns.

Word	Noun	Adjective	Verb	Adverb
legionary	Yes	No	No	No
legionnaire	Yes	No	No	No

As nouns, legionary and legionnaire are synonyms defined as:

legionary and legionnaire: a soldier who is a member of a legion (especially the French Foreign Legion)

legionary (noun)	legionnaire (noun)
a soldier who is a member of a legion (especially the French Foreign Legion)	a soldier who is a member of a legion (especially the French Foreign Legion)