I don't know why but for some reason when I got on the train that
day it was unusually full, something I don't recall ever happening in
the past.
As for the above sentence, I have some questions:
-
Is why a conjunction or adverb? My own understanding is that why is an adverb here which modifies the verb know, and but is the conjunction which connects two clauses. Is that true?
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As I read on Grammarly.com, when but is joining two independent clauses, we need to put a comma before it. Otherwise, leave the comma out. According to this rule, the two clauses are 'I don't know why' and 'for some reason when I got on the train that day it was unusually full, something I don't recall ever happening in the past.' But since there is no comma and the second clause doesn't express a complete thought, the second clause is a dependent clause or subordinate clause. Is that right?
-
someone told me that the whole sentence is an object clause after why, but if the above clues are correct, then the sentence is not a object clause.
Best Answer
The general form "I don't know [question word], but" is a common idiomatic expression. The overall intent is to indicate some measure of surprise at an unexpected or unusual situation.
And so on. I would memorize and practice it like any other idiomatic expression, as a complete phrase, since the individual words are not as important.