English — Time conjunctions
Words like when, while, before, after, until, since and as soon as join two clauses and say when the action happens. The key rule: in a clause about the future, use the present tense, not will — I'll call you when I arrive, not when I will arrive.
How it works
The time clause can come first or second: When it rains, we stay in = We stay in when it rains. For the future, keep the present in the time clause and will in the main clause: As soon as she calls, I'll leave. For an action already finished before another, use the present perfect after by the time or after: After I've eaten, I'll help you. With as you often stress two things happening together: As I left, it started to snow.
Examples
| Conjunction | Use and tense | Example |
|---|---|---|
| when | at the time that; use the present for the future | I'll call you when I arrive. |
| while | during the same time; often with a continuous tense | She read while I was cooking. |
| as | just as two things happen together | As I opened the door, the phone rang. |
| before / after | one action earlier / later than another | Wash your hands before you eat. We left after it stopped. |
| until / till | up to the moment when something happens | Wait here until the rain stops. |
| since | from a past point until now; with the present perfect | I've lived here since I was ten. |
| as soon as | immediately when; present for the future | Call me as soon as you get home. |
| by the time | before another moment; often with the past perfect | By the time we arrived, the film had started. |
Good to know
The most common mistake is putting will in the time clause: not I'll call you when I will arrive, but I'll call you when I arrive. The same holds after as soon as, before, after, until and by the time: As soon as it stops raining, we'll go — never when it will stop.