centenary vs centennial

centenary and centennial both are nouns.

Word	Noun	Adjective	Verb	Adverb
centenary	Yes	Yes	No	No
centennial	Yes	Yes	No	No

As adjectives, centenary and centennial are synonyms defined as:

centenary and centennial: of or relating to or completing a period of 100 years

As nouns, centenary and centennial are synonyms defined as:

centenary and centennial: the 100th anniversary (or the celebration of it)

centenary (noun)	centennial (noun)
the 100th anniversary (or the celebration of it)	the 100th anniversary (or the celebration of it)

centenary (adjective)	centennial (adjective)
of or relating to or completing a period of 100 years	of or relating to or completing a period of 100 years