Clause
A subordinate clause also called a dependent clause is one which cannot stand by itself. This is because it does not express a complete thought. It contains both a subject and a verb. A subordinate clause always depends on a main clause. The main clause is almost always an independent clause, therefore the main clause by itself makes sense and can stand on its own. However, the subordinate clause does not. For example, I love you makes perfect sense left on its own. However, and always will, does not. The only time a sentence can be made up of only dependent clauses is when they are joined by correlative conjunctions: conjunction pairs like "either/or", "neither/nor", and "not only/but also".