A2 · Elementary

when, while, before, after, until and as soon as

These words begin a time clause. The time clause says when the main action happens. In a time clause about the future, use a present tense, not will.

The main idea

A time clause answers the question when. On this page the time clause is a full clause with a subject and a verb, and it needs a main clause. You can put the time clause first or second. When the time clause is first, put a comma after it.

When the lesson ends, we pack our bags.
We pack our bags when the lesson ends.

When, while and as

Word	Use	Example
when	one event at a point in time	When the lecture finished, everyone left.
while	a longer action in progress	I read while I was on the train.
as	two things happening at the same time	As the children were playing, their parents talked.

When can also introduce a single completed event inside a longer activity: She was cycling home when the storm started.

Before and after

Charge your phone before you leave.
After the shops close, the street gets quiet.
I check the address before I send a message.

Before and after can also be prepositions with an -ing form: before eating, after leaving. See Preposition + -ing: look forward to, interested in, instead of.

Until

Until means "up to the time when". The until-clause normally comes after the main clause.

The shop stays open until nine o'clock.
Don't open the door until the car stops.
We waited until the rain stopped, and then we left.

Present tense for the future

When the main clause is about the future, the time clause uses a present tense. Do not use will in the time clause.

We will send you a message when we arrive.
The show will start after the lights go down.
I will message you as soon as I have finished. present perfect: one action finishes before the other

The present perfect shows that one action is complete before the other starts. The present simple is also possible.

As soon as, once and by the time

As soon as means "immediately after". Once means "from the time when something happens or is true". By the time means "at or before the time when"; the earlier event often takes the past perfect.

Text me as soon as the plane lands.
Once you are ready, we can leave.
Once you have paid, your ticket arrives by email.
By the time we got to the station, the train had left.

Watch out

✗When the package will arrive, I will let you know.

✓When the package arrives, I will let you know.

Do not use will in the time clause; use the present simple.

✗I will see you as soon as I will finish.

✓I will see you as soon as I finish.

Use the present simple after as soon as, not will.

✗The builders must finish the roof until next week.

✓The builders must finish the roof by next week.

For a deadline, use by, not until: the work finishes once, before that time.

What comes next

See Future time clauses: when, as soon as, if and until for more on future time clauses, Past continuous or past simple? for while and when in the past, and during, for and while for during and for.

Practice

Eight questions. Choose one answer for each.