Olympiad vs Olympics

Olympiad and Olympics both are nouns.

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

As nouns, Olympiad and Olympics are synonyms defined as:

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

Other synonyms of Olympiad include Olympic Games.

Olympiad (noun)	Olympics (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