Russian IS an adjective.
Yes, Russian can be a proper adjective for things and people from Russia. But it can also be a proper noun (demonym) for a person from Russia (one Russian, two Russians).
To turn "Russia" into an adjective, you can add "-n" to the end, resulting in "Russian." For example, you could say the "Russian culture" or the "Russian language" to describe attributes related to Russia.
The proper adjective for Portuguese is "Portuguese."
Mayan is itself a proper adjective.
The proper adjective for Mexican is "Mexican."
Yes, Russian can be a proper adjective for things and people from Russia. But it can also be a proper noun (demonym) for a person from Russia (one Russian, two Russians).
To turn "Russia" into an adjective, you can add "-n" to the end, resulting in "Russian." For example, you could say the "Russian culture" or the "Russian language" to describe attributes related to Russia.
The proper noun Russians is plural; people of or from Russia. The singular form is Russian, which is also the proper adjective.
The proper noun Russians is plural; people of or from Russia. The singular form is Russian, which is also the proper adjective.
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 George is Georgian.
The proper adjective for Siam is Siamese.
Mayan is itself a proper adjective.
Freudian is the proper adjective for Freud.