Is when a subordinate conjunction?

It would be fragment. That's the nature of dependent clauses. Only independent clauses can stand alone. Unlike coordinating conjunctions, which connect independent clauses in a balanced, coordinated way, subordinating conjunctions attach themselves to a clause and subordinate it to the rest of the sentence.Jul 1, 2013 read more

The essential ingredient in a complex sentence is the subordinate conjunction: The subordinate conjunction has two jobs. First, it provides a necessary transition between the two ideas in the sentence. This transition will indicate a time, place, or cause and effect relationship. read more

In a complex sentence, the role of the subordinating conjunction and the dependent clause is to establish a time, a place, a reason, a condition, a concession, or a comparison for the main clause. The subordinating conjunction provides the bridge between the main clause and the dependent clause. read more