This is the 1176th most frequent Portuguese word.
chinês
Chinese.
In this sentence, 'chinês' is used as a noun to refer to the Chinese language.
Eu quero aprender chinês.
I want to learn Chinese.
Here, 'chinês' acts as an adjective to describe the nationality of the boy, indicating that he is from China.
Aquele rapaz é chinês.
That boy is Chinese.
In this case, 'chinês' is used as an adjective to describe the book, indicating its origin or type as being related to China.