The order of words in questions in English is different from the order of words in subordinate clauses (i.e. sentences starting with expressions like “the place where …”, “the time when …”, “the man who …”, etc.). This often causes problems for students because both types of sentences typically begin with the same words (“where”, “when”, “who”, “how”, etc.).
The rule of thumb, however, is this: The order of words in subordinate clauses is the same as in regular announcement clauses, e.g.:
- I don’t know why he goes there. (correct)
- I don’t know why does he go there. (incorrect)
Of course, this is true in all tenses, not just the present:
- I don’t know why she did it. (correct)
- I don’t know why did she do it. (incorrect)
- I don’t know why she has done it. (correct)
- I don’t know why has she done it. (wrong)
Many students who would not make a mistake in the above examples make a mistake with the verb “to be”. However, the same rule applies there too:
- I don’t know where it is.
- I don’t know where is it. (incorrect)
- I don’t know how he is doing it. (correct)
- I don’t know how is he doing it. (wrong)
Subordinate clauses that are part of the question
It gets a little more confusing when the subordinate clause is part of the question. The rule is still the same: the word order in the subordinate clause is the same as in the announcement clause. We must remember that what makes a question a question is the main clause (underlined in the following examples), not the subordinate clause:
- Do you know why she did it? (correct)
- Do you know why did she do it? (incorrect)
- Do you know who he is? (correct)
- Do you know who is he? (wrong)
The structure is slightly different when we ask for the subject (i.e. when the subject of the subordinate clause is directly “who” or “what”), but the logic is still the same:
- Do you know who went there? (correct)
- Do you know who did go there? (incorrect)