Vietnam vs Annam

Vietnam and Annam both are nouns.

Word	Noun	Adjective	Verb	Adverb
Vietnam	Yes	No	No	No
Annam	Yes	No	No	No

As nouns, Vietnam and Annam are synonyms defined as:

Vietnam and Annam: a communist state in Indochina on the South China Sea; achieved independence from France in 1945

Other synonyms of Vietnam include Socialist Republic of Vietnam, Viet Nam.

Vietnam (noun)	Annam (noun)
a prolonged war (1954-1975) between the communist armies of North Vietnam who were supported by the Chinese and the armies of South Vietnam who were supported by the United States	a communist state in Indochina on the South China Sea; achieved independence from France in 1945
a communist state in Indochina on the South China Sea; achieved independence from France in 1945