when, before, after, until

These words start a time clause: a part of the sentence that says when the main action happens.

• when: at the same time, or straight after
• before: earlier than the other action
• after: later than the other action
• until: up to that time, then it stops

The time clause can come first or second. When it comes first, put a comma after it.

No will after them

When the sentence is about the future, the time clause still takes the present simple, not will. Will goes in the main part only.

Before and after with -ing

After before and after you can also use a verb with -ing, with no subject, when the subject is the same.

Until or by

Until says that something goes on up to a time. By says that something happens at or before a time.

Common mistakes

• × I'll call you when I will get home. → I'll call you when I get home.
• × Before you will leave, … → Before you leave, …
• × Wait until I will come back. → Wait until I come back.
• × I'll finish it until Friday. → I'll finish it by Friday.