Macao vs Macau

Macao and Macau both are nouns.

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

As nouns, Macao and Macau are synonyms defined as:

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

Macao (noun)	Macau (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