Subordinating Conjunctions

Subordinating conjunctions introduce a dependent clause and attach it to an independent clause, forming a complex sentence. Unlike coordinating conjunctions, which link two equals, a subordinating conjunction makes one clause subordinate to — dependent on — the other. This is how English expresses nuanced relationships such as cause, time, condition, and concession.

The common subordinating conjunctions fall into clear semantic categories. Cause includes because, since, and as — I stayed home because I was tired. Time includes after, before, when, while, until, as soon as, and once — Call me when you arrive. Condition includes if, even if, unless, as long as, in case, and provided that — You can borrow the car if you fill the tank. Concession includes although, though, even though, whereas, and while — Although it rained, we enjoyed the picnic. Purpose includes so that and in order that — She spoke slowly so that everyone could understand. Place includes where and wherever — Sit wherever you like.

The position of the dependent clause is flexible, which gives you stylistic control. When the dependent clause comes first, separate it from the main clause with a comma: Since we were out of milk, I went to the supermarket. When the independent clause comes first, no comma is needed: I went to the supermarket since we were out of milk. This rule is one learners should internalize early, because missing the comma after an introductory dependent clause is a common error.

A subtle but important contrast exists between subordinating conjunctions and relative pronouns (who, which, that). Both introduce dependent clauses, but relative pronouns replace a noun inside their clause, while subordinating conjunctions do not: compare The book that I read (relative pronoun, replaces the object) with I read because I was curious (subordinating conjunction, no noun replaced). Similarly, subordinating conjunctions differ from conjunctive adverbs like however or therefore, which join independent clauses and require semicolons: I was tired; therefore, I stayed home versus I stayed home because I was tired.

For learners, the priority is mastering the big four categories — cause, time, condition, and concession — since they cover the vast majority of real-world use. Practise identifying the dependent clause and asking yourself what relationship the conjunction signals. Once you can reliably answer "Is it giving a reason? A time? A condition?" you have understood subordination.