Olympics vs Olympiad

Olympics and Olympiad both are nouns.

Word	Noun	Adjective	Verb	Adverb
Olympics	Yes	No	No	No
Olympiad	Yes	No	No	No

As nouns, Olympics and Olympiad are synonyms defined as:

Olympics and Olympiad: the modern revival of the ancient games held once every 4 years in a selected country

Other synonyms of Olympics include Olympic Games.

Olympics (noun)	Olympiad (noun)
the modern revival of the ancient games held once every 4 years in a selected country	the modern revival of the ancient games held once every 4 years in a selected country
	one of the four-year intervals between Olympic Games; used to reckon time in ancient Greece for twelve centuries beginning in 776 BC