No, the word Maria is a proper noun. It is a female given name.
Maria is not an adjective. It's a proper noun and should always be capitalized.
The proper adjective for Portuguese is "Portuguese."
Mayan is itself a proper adjective.
Russian IS an adjective.
The proper adjective for Mexican is "Mexican."
Maria is not an adjective. It's a proper noun and should always be capitalized.
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.
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.
The proper adjective for Antigua is Antiganantigan