semicentennial vs semicentenary

semicentennial and semicentenary both are nouns.

Word	Noun	Adjective	Verb	Adverb
semicentennial	Yes	Yes	No	No
semicentenary	Yes	Yes	No	No

As adjectives, semicentennial and semicentenary are synonyms defined as:

semicentennial and semicentenary: of or relating to or marking the 50th anniversary

As nouns, semicentennial and semicentenary are synonyms defined as:

semicentennial and semicentenary: the 50th anniversary (or the celebration of it)

semicentennial (noun)	semicentenary (noun)
the 50th anniversary (or the celebration of it)	the 50th anniversary (or the celebration of it)

semicentennial (adjective)	semicentenary (adjective)
of or relating to or marking the 50th anniversary	of or relating to or marking the 50th anniversary