Subordinating conjunctions begin dependent clauses. A dependent clause has a subject and a verb, but it cannot stand alone as a complete sentence. It needs a main clause to finish the idea. In Because it was raining, the clause gives information, but it leaves the listener waiting for the rest of the sentence. In Because it was raining, we stayed inside, the main clause completes the meaning.

These conjunctions create a close relationship between two ideas. The second idea depends on the first one for full meaning, so the clause introduced by the conjunction cannot be used by itself in normal writing. For more on how clauses work, see Clauses. The way the two clauses fit together also depends on Word Order.

Starting dependent clauses with conjunctions

Idea
A subordinating conjunction introduces a dependent clause that cannot stand alone.
A dependent clause needs a main clause to make a complete sentence.
The dependent clause can come before or after the main clause.

When, while, before, after, and as soon as connect actions in time. They show when one event happens in relation to another event. When points to a time at which something happens: Call me when you arrive. While links two actions happening at the same time: She read while he cooked.

Before shows an earlier action, and after shows a later one: Wash your hands before you eat and We talked after the meeting. As soon as shows that one action happens immediately after another: As soon as the bell rang, the students left. These time linkers are common in everyday speech and writing, and they are especially useful in time expressions in Present Tense and Time Clauses.

Common time linkers in sentences

Usage	Explanation
Simultaneous action	Use while to show that two actions happen at the same time.
Earlier action	Use before to show that one action happens earlier than another.
Later action	Use after to show that one action happens later than another.
Immediate follow up	Use as soon as to show that one action happens right after another.
At the same time	Use when to show that one event happens at the same moment as another.

Because and since introduce a reason. They answer the question why. Because usually gives a new reason or the main reason the listener needs to know: We left early because the train was crowded.

Since often gives a reason that is already known, expected, or easy to accept from the situation: Since you are here, you can help me. In formal writing, since can sound a little more direct or polished than because, but both forms are correct. The reason clause can come before or after the main clause, and the meaning stays the same. In Since the office is closed, we will return tomorrow, the reason appears first and leads into the result.

Giving reasons with cause clauses

Usage	Explanation
Direct reason	Use because when you give a clear reason for something.
Shared reason	Use since when the reason is already known or easy to accept.
New information	Use because when the reason is the important new information.

Although and though introduce a contrast. They show that one idea is true, but another idea is also true. Although it was late, they kept working. The first clause sets up an expectation, and the second clause goes against that expectation.

Though means the same thing as although and is common in spoken English. It often sounds a little less formal. Both conjunctions can appear at the start of a sentence or in the middle of a sentence. Although he was tired, he finished the report and He finished the report although he was tired are both natural. These contrast clauses help connect ideas clearly in larger sentence patterns and support accurate punctuation in Punctuation.

Showing contrast in sentences

Usage	Explanation
Formal contrast	Use although to show contrast in a more formal way.
Everyday contrast	Use though to show contrast in everyday speech.
Sentence end contrast	Use though at the end of a sentence to add a contrast idea.

If introduces a condition. The main clause depends on whether the condition happens or is true. If it rains, we will stay home. This pattern is common for real or possible situations. It can also appear with imagined situations: If I had more time, I would travel more.

Unless means if not. It introduces a negative condition: We will miss the bus unless we leave now means We will miss the bus if we do not leave now. The clause with unless usually describes the condition that must happen to avoid the result. In everyday English, if and unless are some of the most useful subordinating conjunctions for decisions, plans, and warnings.

Conditions with if and unless

Idea
Use if to show that one result depends on a condition.
Use unless to mean if not.
In real conditions, if can describe a likely future result.
In hypothetical conditions, if can describe an imagined situation.

A dependent clause usually comes before or after the main clause. In both positions, the conjunction stays at the start of the dependent clause: When the movie ended, we went home and We went home when the movie ended. The word order inside each clause follows normal English sentence order, with subject + verb in each clause.

A comma usually appears when the dependent clause comes first. It separates the opening clause from the main clause and makes the sentence easier to read. When the main clause comes first, the comma is usually not needed: We went home when the movie ended. This pattern is standard in English and fits naturally with sentence structure in Word Order.

Word order and punctuation with clauses

Idea
When the dependent clause comes first, use a comma before the main clause.
When the main clause comes first, the comma is usually not needed.
The dependent clause can appear before or after the main clause without changing the meaning much.

So that and in order that express purpose. They explain why someone does something. So that is common in speech and writing: She wrote the number down so that she would not forget it. In order that is more formal and less common in everyday conversation: The report was saved in order that everyone could review it later.

These clauses usually work with a subject + verb form after the conjunction. The purpose clause often uses a modal verb such as can, could, will, or would. The main clause gives the action, and the purpose clause explains the goal. These patterns also work with other purpose expressions in Conjunctions and are useful for clear sentence structure in Sentence Structure.