an English essay

[yuhan]

an English essay
Does it mean "an essay written in English" or "an essay on the English language"?
Thanks a lot.

[chester_100]

I think you're referring to ambiguity. Look at these:

-He is an English history teacher = he teaches English history, and he may not be English.
-He is an English history teacher = he teaches history and he is English.

About your case, I would say it means 'an essay written in English', because we can use other structures to convey 'an essay about English'. For example, as you have mentioned, we simply could say 'An essay onthe English language'.

[Tdol]

There could be contexts where it could mean an essay about the English language, but I agree with Chester and would normally take it as the language it was written in.