Proper Adjectives are formed from proper nouns and modify nouns and pronouns.
I love Greek culture
A proper noun is the specific name used for any person, place, or thing. Proper adjectives typically look like their original proper nouns but have some sort of alternative ending in order to make them adjectives.
He lives in America. (proper noun)
He likes American food. (proper adjective)
Proper adjectives are derived from proper nouns. For this reason they are capitalised.
When she lived in China, Jane ate a lot of Chinese food. (Of course in China they just call it food.)
When a proper adjective has a prefix, the prefix itself is never capitalised (unless it is the first word of the sentence). However, the proper adjective itself is still capitalised.
In pre-Columbian America corn was the only cultivated cereal.
The most common endings for nationalities are -ian/-ean/-an, -ic, -ish.
The reason that the English language has so many endings for different nationalities is that they were borrowed from other languages.
-ian/-ean/-an | -ic | -ese | -i | -ish |
Italian | Icelandic | Chinese | Iragi | Danish |
Korean | Nordic | Japanese | Israeli | Finnish |
Moroccan | Hispanic | Portuguese | Pakistani | Irish |