A proper adjective functions the same as any other adjective by modifying a noun or, occasionally, a pronoun. The difference between a proper adjective and other adjectives is that it is formed from a proper noun. Just like a proper noun must begin with a capital letter, so too must a proper adjective.
Deriving Proper Adjectives from Proper Nouns
Many of the most familiar proper adjectives are derived from the names of places like countries or cities.
I can’t wait to try some authentic New York pizza.
Our neighbors moved here from the Italian countryside.
Respect and orderliness are hallmarks of Japanese culture.
The African plains are home to many beautiful animals.
Buffalo chicken is the best.
All of the underlined adjectives above are derived from the proper names of places. Be especially careful with those that do not change form when being used as an adjective. While some place names like New York and Buffalo from the examples above might look the same in their adjective and noun forms, others may change. For example, Paris becomes Parisian when formed into an adjective.
Other common proper adjectives come from proper nouns like the names of people, brands, or even religions.
We saw several Shinto shrines on our trip to Japan.
I got a new Dell laptop last summer.
The Merovingian rein ended in the 700s.
The virtuous old governor was never accused of engaging in Machiavellian politics.
Miss Allen’s favorite type of poem is the Shakespearean sonnet.
It is also important to keep in mind that prefixes attached to proper adjectives require a hyphen and are not capitalized.
The chairman was forced to resign for his anti-Korean remarks at the press conference.
A dislike for apple pie is just un-American.
Adjectives Formerly Considered Proper
Although many adjectives formed from proper nouns are proper adjectives, some have been in use for so long that they no longer rely on their proper noun counterparts for their meanings to be understood. Since they have become completely separate words in their own right, they are no longer considered proper adjectives and no longer need to be capitalized.
It took herculean effort to move the heavy old desk.
The captain performed his difficult assignments with stoic resolve.