A complex sentence has one main clause and one subordinate clause. The main clause can stand alone as a sentence. The subordinate clause cannot stand alone and adds extra information to the main clause.

A main clause gives a complete idea. It has a subject and a verb, and it can be a full sentence by itself. In a complex sentence, the main clause carries the central meaning.

A subordinate clause also has a subject and a verb, but it does not give a complete idea alone. It depends on the main clause. It adds information about reason, time, condition, or contrast.

The subordinate clause can come before or after the main clause. Both orders are possible in complex sentences. The meaning stays connected in both positions.

A subordinate clause with because gives the reason for the action or situation in the main clause. It explains why something happens. This pattern joins a result and its cause in one sentence.

A subordinate clause with when shows the time of the action in the main clause. It connects two actions or situations in time. This pattern helps show when something happens.

A subordinate clause with if shows a condition for the main clause. The action in the main clause depends on that condition. This pattern shows that one thing happens only in a certain situation.

A subordinate clause with although shows contrast with the main clause. The two parts show different or unexpected ideas together. This pattern joins ideas that do not match in an expected way.

You can now understand and build complex sentences with a main clause and a subordinate clause. You can use because, when, if, and although to show reason, time, condition, and contrast. You can also place the subordinate clause at the beginning or end of the sentence and use a comma when it comes first.