ex) She is an English teacher.

English teacher is a compound noun. When we stress the first noun, 'English', it means that she teaches English as a teacher.
However, when we stress 'teacher', 'English' is used as an adjective. In this case, 'English teacher' means a teacher from England.
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Is the explanation grammatical? Would you check them?

I don't know what happens in England, but no matter how you pronounce the term in the US, the assumption would be that she teaches English. If you want to be sure it's understood that she is a teacher in England, then you'd have to say just that: She is a teacher in England.

=)

Yes, the explanation is grammatically correct. The explanation accurately describes how the compound noun "English teacher" can have different meanings depending on which part of the compound is stressed. When the stress is on the first noun "English," it indicates that she teaches the subject of English. On the other hand, when the stress is on the second noun "teacher," it indicates that she is a teacher from England.