Subordinating conjunctions introduce a dependent clause and connect it to an independent clause. They show how one idea depends on another by adding a relationship such as time, cause, condition, contrast, purpose, or concession. The dependent clause cannot stand alone as a complete sentence, so it needs the main clause to complete the meaning.

A dependent clause can come before or after the independent clause. When the dependent clause comes first, it sets context and the main clause delivers the key point. When it comes second, it adds an explanation or condition after the main idea.

Rule	Example
If the dependent clause comes first, use a comma after it	Because it was raining, we stayed inside.
If the dependent clause comes after the main clause, usually no comma	We stayed inside because it was raining.
Use a comma before the dependent clause mainly when it is nonessential or strongly contrastive	I went anyway, although I was tired.

Time subordinators explain when something happens relative to something else. They can show sequence, simultaneity, or a deadline. Choose the conjunction that best matches the timing relationship you want to express.

Word/Phrase	Definition	Example
when	at the time that	Call me when you arrive.
while	during the same time as	I read while she cooked.
before	earlier than	Wash your hands before you eat.
after	later than	We left after the meeting ended.
until	up to the time that	Stay here until I come back.
as soon as	immediately when	Text me as soon as you land.
since	from a past time until now or then	I have felt better since I started sleeping more.

Reason subordinators explain why something happens. They can sound neutral, formal, or emphatic depending on the word choice. Use them to connect a result in the main clause to a cause in the dependent clause.

Word/Phrase	Definition	Example
because	direct reason	I left early because I felt sick.
since	reason that is already known or background	Since you are here, let us begin.
as	mild or background reason	As it was late, we went home.
now that	reason based on a new situation	Now that you have finished, you can rest.

Conditional subordinators set a requirement for the main clause to be true. They can describe real possibilities, limits, or exceptions. The dependent clause expresses the condition and the main clause expresses the result.

Word/Phrase	Definition	Example
if	basic condition	If it rains, we will cancel.
unless	negative condition meaning except if	We will go unless it rains.
provided that	strict condition often used for rules	You may leave provided that you finish your work.
as long as	condition emphasizing duration or limits	You can borrow it as long as you return it today.
even if	result stays the same despite the condition	I will go even if it is snowing.

Concession subordinators show that the main clause is true even though the dependent clause presents a contrast. They are useful for balancing two ideas that do not align in the expected way. Choose a word that matches how strong the contrast is and how formal you want to sound.

Word/Phrase	Definition	Example
although	contrast with a clear concession	Although I was tired, I finished the report.
though	similar to although, often more conversational	I liked the movie, though it was long.
even though	strong concession	Even though it was expensive, we bought it.
whereas	contrast between two facts	She likes tea, whereas I prefer coffee.
while	contrast between two facts, also used for time	While the plan is simple, it is not easy.

Purpose subordinators explain the goal of an action in the main clause. They answer the question why someone does something, focusing on intention rather than cause. They are common in instructions, plans, and formal writing.

Word/Phrase	Definition	Example
so that	with the purpose that	I saved the file so that I could send it later.
in order that	formal version of so that	She spoke quietly in order that the baby would not wake.
so	informal purpose, often before an adjective or phrase	I left early so I would not miss the train.

Some subordinating conjunctions present a result that follows from the main clause. This is different from reason: the dependent clause shows the outcome, not the cause. These forms often emphasize the strength or extent of the main clause.

Word/Phrase	Definition	Example
so that	can also introduce a result, depending on meaning	He whispered so that nobody heard him.
so plus adjective that	result of a degree or intensity	The test was so hard that many students failed.
such plus noun that	result of a type or kind	It was such a good meal that we ordered dessert.

Subordinating conjunctions create an unequal relationship: one clause depends on the other. Coordinating conjunctions create an equal relationship between two independent clauses. Knowing the difference helps you punctuate correctly and choose structures that match your meaning.

Rule	Example
Subordinating conjunction plus dependent clause cannot stand alone	Because I was late is incomplete.
Coordinating conjunction links two independent clauses	I was late, but I still came.
Subordination often answers a specific question about the main clause	I stayed home because I was sick answers why.

Many subordinating conjunctions have close substitutes that differ mainly in tone. Some are more formal and common in academic or legal contexts, while others are more conversational. Choosing an appropriate conjunction helps your writing sound natural for the situation.

Word/Phrase	Definition	Example
because	neutral, common in speech and writing	I stayed because I wanted to help.
since	slightly more formal or backgrounded reason	Since the data is incomplete, we will wait.
provided that	formal and conditional, common in rules	You may enter provided that you show ID.
though	more conversational concession	It is expensive, though it lasts a long time.