Amazonian is the proper adjective for Amazon.
The proper adjective form for Amazon is Amazonian, such as the Amazonian rain forest.
Large and varied are both adjectives. South would be an adjective if it were not part of a proper noun. Amazon is likely a noun adjunct here, but Amazonian would be a proper adjective.
Vietnamese is the proper adjective for Vietnam.
The proper adjective for George is Georgian.
The proper adjective for Siam is Siamese.
No, old is not a proper adjective. A proper adjective is an adjective derived from a proper noun, such as Swiss cheese, Bolivian pottery, Chinese silk, etc.
France is always a proper noun it is never a proper adjective (what is a proper adjective? The adjective is french. I like french food
The proper adjective for Antigua is Antiganantigan
A proper adjective is a descriptive word derived from a proper noun.Some examples are:Asia (proper noun) - Asian (proper adjective)Brazil (proper noun) - Brazilian (proper adjective)Canada (proper noun) - Canadian (proper adjective)Elizabeth I (proper noun) - Elizabethan (proper adjective)Sigmund Freud (proper noun) - Freudian (proper adjective)George Orwell (proper noun) - Orwellian (proper adjective)Proper nouns and proper adjectives are always capitalized.
Kuwaiti is the proper adjective for Kuwait.
Oklahoman is the proper adjective for Oklahoma.