Is it wrong to say, "He is a Japanese" or "He is a Chinese"?
A person I know told me that "Japanese" and "Chinese" are adjectives, and we should say, "He is Japanese" or "He is Chinese" (without "a").
According to Longman English Grammar (G. Alexander), 2.27 Nouns with the same singular and plural forms, Some nouns do not change in form. These include:
- certain nouns describing nationalities e.g., a Chinese, a Swiss, a Vietnamese
He is a Vietnamese
This grammar book introduces an example: Nakamurasan is (a) Japanese.
I took this that "a" is optional.
Does it mean it is grammatically okay to put "a," but it sounds unnatural to native speakers these days?
Forms like a Japanese exist, but they are not very common nowadays, and forms like Spaniard and Finn where there were special nouns are heard less. I think that people are more careful about their choice of terms and may avpoid these in case they seem less polite.
This is one of the fuzzy areas of English. When we have a separate word for the person, there is no problem – My sister is engaged to a Finn/Pole/Dane. (Though we usually use BE + adjective to talk about nationality: He is Finnish/Polish/Danish).
We use some adjectives, especially if they end in –(i)an as a noun for the person: My sister is engaged to a German/an Australian; He is German/Australian .
For other adjectives, we add –man or –woman: My sister shares a flat with a Frenchwoman/Irishman.
Some adjectives, particularly those ending in –ese can be used as a noun, though some people feel uncomfortable with these: (?) My sister is engaged to a Swiss/Chinese/Japanese. He is Swiss/Chinese/Japanese.
ps: While I was writing this response, Tdol posted his, but I'll post this anyway.
Just to confirm how arbitrary this is, I agree with Tdol that Spaniard appears to be impolite. I am happy with Finn and unsure about Turk and Pole.