Subordinating Conjunctions

A subordinating conjunction connects a dependent clause to an independent clause. The independent clause expresses a complete thought on its own. The dependent clause cannot — it needs the main clause to make sense.

Here because it was raining is the dependent clause. Remove the main clause, and it becomes a fragment: Because it was raining. — the reader waits for more.

This is the key difference from coordinating conjunctions like and, but, and or. Coordinating conjunctions join two equal, independent parts. Subordinating conjunctions make one clause depend on the other, creating a hierarchy: the main idea sits in the independent clause, and the supporting detail sits in the dependent one.

The comma rule

The punctuation depends on clause order.

Dependent clause first — use a comma.

Independent clause first — usually no comma.

The logic is straightforward: when the dependent clause opens the sentence, the comma marks where the main clause begins. When the main clause comes first, the reader doesn't need that signal.

Categories of subordinating conjunctions

Subordinating conjunctions fall into several groups based on the relationship they express. Below is a map of the main categories with a few examples in each. Each category is covered in depth in later lessons — here the goal is to see the full picture.

Time

These conjunctions place events on a timeline relative to each other.

Common words: when, while, before, after, until, since, as soon as, once

Reason

These explain why something happens.

Common words: because, since, as

Note that since and as can also express time. Context makes the meaning clear: Since you left (time) vs. Since you're here (reason).

Contrast and concession

These introduce something unexpected — the dependent clause contradicts or qualifies the main idea.

Common words: although, though, even though, while, whereas

Condition

These set a requirement or scenario that must be true for the main clause to apply.

Common words: if, unless, provided that, as long as

Purpose

These explain the goal or intention behind an action.

Common words: so that, in order that

In everyday speech, so that is far more common. In order that appears mostly in formal writing.

Result

This pattern uses so + adjective/adverb + that to express a consequence.

The adjective or adverb sits between so and that, forming a single construction.

Words with double duty

Several subordinating conjunctions belong to more than one category, depending on context.

This is rarely confusing in real sentences. The surrounding words make the intended meaning obvious.

Common mistakes

Missing comma after a fronted dependent clause

Adding a comma before the conjunction when the main clause comes first

Using a subordinating conjunction as a full sentence

Confusing if and unless