But I've heard from a teacher thatA assumes you don’t know of him. The assumes you do.
Yes, it’s wrong. Or you misunderstood. However, if you use an article to modify the man’s name, rather than his description, that’s another matter. If you call someone “a John Smith”, then you do imply that he may be one of a number of people of that name (or that he’s just some random person who happens to have that name). But you’d then have to use a clause to describe his occupation; for example: a John Smith, who is a professor.But I've heard from a teacher that The English professor means there's only one English professor named John Smith who said that
An English professor means there are more than one English professors named John Smith. And he is one of them.
Is it wrong?
Your explanation in post #3 is misguided. This has nothing to do with there being more than one person called John Smith. That would be expressed differently (see #5).I am somehow mixing the ideas of #2 and #3, don't know how to tackle this.
Let's start with syntax first. Notice that the following is debatable:John Smith, an/the American English professor, said that we should use a question mark at the end of a question.
What's the difference between a and the here?