Why

Yes. I'm not sure that "why" is a conjunction though.

GPYYes. I'm not sure that "why" is a conjunction though.

Thanks for the reply. I think that it is rather a conjunction connecting two main clauses. In my opinion, why cannot be treated as a relative pronoun that here thus making the why I left a subordinate clause.

Most serious writers avoid "reason/why" and "reason...because" constructions.

tkacka15Thanks for the reply. I think that it is rather a conjunction connecting two main clauses. In my opinion, why cannot be treated as a relative pronoun that here thus making the why I left a subordinate clause.

Oxford Dictionaries call it a relative adverb:

PhilipMost serious writers avoid "reason/why"

I suppose they also avoid person who, place where and time when.

Thanks for the replies.

Yes, we can replace why with for which thus changing the clause why I left into a subordinate one for which I left/which I left for but as a non-native I somehow can't grasp that why means exactly for which.

tkacka15That's the reason why I left.Can the conjunction why be omitted in the above sentence?

It's not a conjunction, it's an adverb, but yes, it can be omitted

JohnS