What Does a Subordinate Conjunction Do: A Clear 2024 Guide

A subordinate conjunction connects a dependent clause to an independent clause, forming a complex sentence. The dependent clause cannot stand alone—it relies on the main clause to complete its meaning. These conjunctions clarify the relationship between ideas, such as time, cause, contrast, or condition, and help create more expressive, varied sentences.

For example, in the sentence “Because it was raining, we stayed inside,” because is the subordinate conjunction. It introduces the dependent clause “Because it was raining,” which explains why the action in the independent clause—“we stayed inside”—happened. Without the conjunction, the connection between the two ideas would be less clear.

How Subordinate Conjunctions Work

Subordinate conjunctions link clauses of unequal weight. The independent clause expresses a complete thought; the dependent clause adds context but cannot stand alone. The conjunction signals how the two are related.

These words shape meaning by answering questions like when?, why?, under what condition?, or despite what? For instance:

• When the bell rang, class ended. (time)
• She stayed home because she was ill. (cause)
• Although it was cold, they went hiking. (contrast)
• You can go out if you finish your homework. (condition)

Each conjunction guides the reader’s understanding of how the clauses relate. Using the right one improves precision and flow.

Common Subordinate Conjunctions

Some of the most frequently used subordinate conjunctions include because, although, if, when, since, while, unless, and after. Each serves a specific function:

• Because, since, and as indicate cause. (Note: since can also refer to time, so context matters.)
• Although, though, and even though show contrast.
• If, unless, and provided that introduce conditions.
• When, before, after, while, and until relate to time.

Choosing the correct word ensures the intended meaning comes through. For example, “While I was cooking, the phone rang” emphasizes ongoing action, whereas “When the phone rang, I stopped cooking” points to a specific moment.

Sentence Structure and Punctuation

The placement of the dependent clause affects punctuation and emphasis. When the dependent clause comes first, a comma typically follows it:

• Because she studied hard, she passed the test.

When the independent clause comes first, no comma is needed:

• She passed the test because she studied hard.

The difference may seem minor, but it influences rhythm and focus. Starting with the dependent clause puts more weight on the condition, reason, or time frame. Ending with it emphasizes the main action.

This rule applies consistently with most subordinate conjunctions. Following it helps maintain clarity and readability.

Subordinate vs. Coordinating Conjunctions

Subordinate conjunctions differ from coordinating conjunctions in structure and function. Coordinating conjunctions—for, and, nor, but, or, yet, so—join elements of equal grammatical weight, such as two independent clauses:

• He left, and she stayed.

This is a compound sentence. Both clauses can stand alone.

In contrast, subordinate conjunctions join unequal clauses, creating complex sentences:

• He left because he was tired.

Here, “because he was tired” depends on the main clause to make sense. The relationship is hierarchical, not equal.

Confusing the two types can lead to errors like sentence fragments or awkward constructions. For example, “He left but although he was tired” combines a coordinating and a subordinate conjunction incorrectly. Choose one type based on the intended relationship.

Identifying Subordinate Clauses

A subordinate clause begins with a subordinate conjunction and contains a subject and verb, but it is not a complete sentence. To recognize one, look for the conjunction and test whether the clause makes sense on its own.

Take the sentence: “We couldn’t buy milk because the store was closed.”

• The clause “because the store was closed” starts with because, has a subject (the store) and a verb (was closed), but does not express a full thought.
• It depends on “We couldn’t buy milk” to complete the meaning.

Practice spotting these clauses in everyday writing. Over time, identifying them becomes automatic, improving both grammar and comprehension.

Common Errors to Avoid

One frequent mistake is using a dependent clause as a standalone sentence:

• Because it was cold. (incomplete)

This is a fragment. It must be attached to an independent clause:

• Because it was cold, we turned on the heater.

Another error is using the wrong type of conjunction. For example:

• He left but although he was tired. (confusing but and although)

Use either but or although, not both. Each serves the same contrastive function, so combining them is redundant.

Misplaced modifiers can also cause confusion. Consider:

• She almost drove the kids to school every day because of traffic.

This suggests she almost performed the action of driving, not that traffic nearly prevented it. A clearer version would be:

• Because of traffic, she almost didn’t drive the kids to school every day.

Clarity depends on correct structure and word placement.

Key Takeaways

• A subordinate conjunction joins a dependent clause to an independent clause, forming a complex sentence.
• It signals relationships such as time, cause, contrast, or condition between the clauses.
• Common examples include because, although, if, when, and since.
• When the dependent clause comes first, use a comma after it. No comma is needed when the independent clause leads.
• Subordinate conjunctions connect unequal clauses, unlike coordinating conjunctions, which join equal elements.
• Avoid sentence fragments by ensuring dependent clauses are attached to independent ones.
• For reliable grammar guidance, the Purdue Online Writing Lab offers clear, well-organized resources.