Macau vs Macao

Macau and Macao both are nouns.

Word	Noun	Adjective	Verb	Adverb
Macau	Yes	No	No	No
Macao	Yes	No	No	No

As nouns, Macau and Macao are synonyms defined as:

Macau and Macao: a former Portuguese province on the south coast of China and two islands in the South China Sea; reverted to China in 1999

Macau (noun)	Macao (noun)
a former Portuguese province on the south coast of China and two islands in the South China Sea; reverted to China in 1999	a former Portuguese province on the south coast of China and two islands in the South China Sea; reverted to China in 1999