Adverb? Preposition? Particle/Delimiter? Is there a recommended book where I can look up such questions? I couldn't find it in the New Penguin Russian Course book.
2 Answers
It can play a role of either adverb (наречие) - in most of the cases - or, sometimes, conjunction ("союз") pretty much like it counterparts "поэтому", "потому" etc. You can find this information in any decent Russian dictionary.
Sometimes this kind of adverbs are called "местоименные наречия" - as opposed to so-called "знаменательные наречия".
It is an indicative pronoun (указательное местоимение), similar to это, то, того... "Оттого, что..." is a conjunction (союз).
