"Chinese" as an adjective: When used as an adjective to describe something from or related to China, it is not a proper noun. For example:
* Chinese food
* Chinese culture
* Chinese language
"Chinese" as a noun: When used as a noun referring to the people of China or the Chinese language, it is a proper noun and should be capitalized. For example:
* The Chinese are known for their hospitality.
* I am learning Chinese.
"The Chinese" as a collective noun: When referring to the people of China collectively, it is also a proper noun and should be capitalized. For example:
* The Chinese have a rich history and culture.
In summary:
* "Chinese" is NOT a proper noun when used as an adjective.
* "Chinese" IS a proper noun when used as a noun referring to the people of China or the Chinese language.
* "The Chinese" IS a proper noun when used as a collective noun referring to the people of China.