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.
Athenian is a proper adjective for Athens.
Egyptian is a proper adjective.
Persian
The proper adjective for Persia is spelled "Persian." This term is used to describe anything related to Persia, including its culture, language, and people.
No, Egyptian is an adjective used to describe something of or from Egypt (a proper noun). Although Egyptian is an adjective, it is still capitalized.
No, "old" is not a proper noun. It is an adjective used to describe the age of a person, object, or thing.
The proper adjective for southwest is "southwestern."
The proper adjective is Haitian.
The proper adjective for Portuguese is "Portuguese."
Vietnamese is the proper adjective for Vietnam.
The proper adjective for Georgia is Georgian.
The proper adjective for George is Georgian.
Freudian is the proper adjective for Freud.
Mayan is itself a proper adjective.
The proper adjective for Siam is Siamese.
The proper adjective for Antigua is Antiganantigan
Kuwaiti is the proper adjective for Kuwait.