400
That, what, who, whoever, whatever, whenever, how, why,whom, whomever, which, when, whether,whose, after, although as if, as long as, as soon as, as though, because, before, how, if, in order that, since, so that, than, though, unless, until, where, while
What are the introductory words to noun clauses, adjective clauses and subordinating conjuctions.