A subordinating conjunction links a dependent clause to an independent clause. The dependent clause cannot stand alone as a full sentence, but it adds a meaning such as time, reason, contrast, condition, or purpose. The independent clause gives the main statement.

Subordinating conjunctions can show when one action happens in relation to another action. They place one clause earlier, later, at the same time, or up to a limit in time. The choice depends on the time relationship you want to show.

Word or Phrase	Definition
when	It shows that one clause happens at the time of another clause or at the moment something happens.
before	It shows that one clause happens earlier than another clause.
after	It shows that one clause happens later than another clause.
while	It shows that two clauses happen at the same time.
until	It shows that one situation continues up to a time limit.

Some subordinating conjunctions show why something happens. Because gives a clear reason. Since and as can also show reason, but they can sometimes also show time, so the meaning may depend on context.

Word or Phrase	Definition
because	It gives a direct reason for the main clause.
since	It can give a reason, but in some contexts it can also mark time from a starting point.
as	It can give a reason, but in some contexts it can also mean at the same time.

Subordinating conjunctions can show that two ideas are different or unexpected together. Although, though, and even though introduce a contrast with the main clause. Whereas also shows contrast, often by placing two facts against each other.

Word or Phrase	Definition
although	It introduces a contrast between the dependent clause and the main clause.
though	It also introduces contrast and is often close in meaning to although.
even though	It introduces a stronger or more surprising contrast.
whereas	It shows that two facts are different when they are compared.

Some subordinating conjunctions show that one clause depends on another clause. If introduces a possible condition. Unless means except if. Provided that shows a condition that must be met, often with a more formal tone.

Word or Phrase	Definition
if	It introduces a condition that may or may not happen.
unless	It means except if and gives a negative condition.
provided that	It introduces a condition that must be true for the main clause to happen.

Subordinating conjunctions can show the aim of an action. So that and in order that link a clause to the purpose of the main action. In order that is often more formal than so that.

Word or Phrase	Definition
so that	It introduces the purpose of the action in the main clause.
in order that	It introduces purpose and often sounds more formal.
that	It can sometimes introduce purpose after certain structures, but this use is less common and depends on style.

The subordinating clause can come before or after the independent clause. When the subordinating clause comes first, a comma usually separates the two clauses. When it comes second, a comma is usually not used, though style can vary in some cases.

Choose the subordinating conjunction by the relationship you want to express and by which idea you want to place in the dependent clause. Some conjunctions have more than one meaning, so context is important. You can now join clauses to show time, reason, contrast, condition, and purpose with clear sentence structure.