Which one of these sentences is grammatically correct?
- Why did the writer use this word?
- Why does the writer use this word?
Which one of these sentences is grammatically correct?
- Why did the writer use this word?
- Why does the writer use this word?
You would use "did" to indicate a single (or repeated) occurrence of something in the past.
You would use "does" to indicate a repeated or regular occurrence of something in the present.
In this case, either works when talking about a written work. The writer wrote it in the past, but you are reading it in the present. The only difference is your own personal point of view -- are you making this comment from the POV of the writer, or from you as the reader?