The proper adjective for Siam is Siamese.
The proper adjective for George is Georgian.
The proper adjective for Antigua is Antiganantigan
Kuwaiti is the proper adjective for Kuwait.
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.
Amazonian is the proper adjective for Amazon.
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.
The proper adjective for Portuguese is "Portuguese."
The proper adjective for southwest is "southwestern."
The proper adjective for Haiti is Haitian.
Vietnamese is the proper adjective for Vietnam.
The proper adjective for Siam is Siamese.
The proper adjective for Georgia is Georgian.
The proper adjective for Mayan is "Mayan."
The proper adjective for George is Georgian.
Freudian is the proper adjective for Freud.
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.