during, for and while

Start with the form

A noun phrase names something: the rehearsal, our visit or half an hour. A full clause contains a subject and a verb: the band was playing. These words do not all take the same ending.

• We practised for forty minutes.

• Someone knocked during the rehearsal.

• Someone knocked while the band was playing.

For and during are prepositions in these patterns: they come before noun phrases. While is a conjunction: it joins a clause to another part of the sentence. A shorter while-pattern is explained below.

For: how long

Use for with a length of time to say how long something lasts. You can give an exact length or a less exact one, such as a few minutes or a long time. This is duration, not a date when something starts.

• The repair took longer than expected. We waited for ninety minutes.
• I haven't worn these boots for ages.
• Can I borrow your ruler for a moment?

For does not choose the verb tense for you. Use the tense that fits the situation: finished past, a situation continuing up to now, or a future plan.

The present perfect links a past situation to now. It uses have or has with a past participle, a verb form such as rented or known. For can appear with it, but for does not mean that every sentence needs a present perfect verb.

You can sometimes leave out for before a length of time. Both I stayed there for four days and I stayed there four days are possible. Keeping for makes the duration pattern clear. Do not turn this into a rule that every time phrase needs for.

During: when, not how long

During names the event or period in which something happens. It does not by itself measure the length of that action. A short action can happen inside a long event.

• My glasses broke during the school trip.
• We changed seats during the interval.

The trip or interval tells you when. Neither sentence tells you exactly how long breaking the glasses or changing seats took. Compare a period when something happens with the length of an activity inside it.

• We talked for twenty minutes during the lunch break.

For twenty minutes gives the length of the conversation. During the lunch break places it inside a named period. You can use both in one sentence because they give different information.

During can cover the whole period

During does not always mean one short moment. It can describe a situation throughout the period. Read the verb and context as well as the preposition.

• The side entrance stays locked during the performance. It stays locked while the performance is taking place.
• A light went out during the performance. This happened at some point within it.

In the first sentence, the state lasts through the performance. In the second, a single event occurs inside it. The word during alone does not settle how much of the period is involved.

Throughout makes the whole-period meaning explicit. In can replace during with some named periods, such as the summer. These alternatives overlap; they are not wrong simply because you are practising during.

• The gallery displays local photographs throughout the festival.
• We painted the fence during the summer. In the summer can also fit here.

During or for with time phrases?

To measure a bare length, use for, not during: for nine days, for half an hour. But do not make the rule "during can never come before a number". A phrase can identify a particular part of an event instead of measuring how long one action lasts.

• The equipment failed twice during the first ten minutes of the lesson.
• The equipment worked for ten minutes before it failed.

During the first ten minutes locates the two failures inside that opening part. For ten minutes measures how long the equipment worked. Cambridge also allows during the last week; last or first can identify the period you are talking about.

Seasons can work with both words, with different meanings. For can give the intended length of a stay; during places an event within the season.

• My aunt rented a room for the summer. The summer was the planned rental period.
• My aunt visited us twice during the summer. The visits happened within that season.

For can also introduce an occasion, as in come home for a birthday. That is a different meaning of for, not a claim that every visit lasts the whole occasion. Keep that separate from the duration contrast.

While: two things happening together

Use while before a clause to show that two situations happen at the same time. One may be the background for the other, or both may continue together.

• I found a missing button while I was sorting the laundry.
• You can use my desk while I'm away.
• The children drew pictures while their uncle read aloud.

A continuous form, such as was sorting, shows an activity in progress. But while does not require a continuous verb. I'm away describes a state; read describes an activity in the last example. Choose a verb form that fits the meaning.

Time-while can also refer to the future. In an ordinary future time clause, use a present form rather than will to predict the future. The main clause can contain will.

• I'll look after the plants while you are away next month.

You can put the while-clause before or after the main clause. Put a comma after it when it comes first.

• While the soup was cooling, I sliced the bread.
• I sliced the bread while the soup was cooling.

Compare the form with during. The meaning can be close, but the ending changes.

Do not put during directly before the full subject-and-verb clause. Do not put time-while directly before an ordinary event noun such as the interview. Use the matching pattern.

Shorter while-clauses (extension)

You can shorten a while-clause when the person doing the activity is clear. With an active -ing form, the person doing that activity should be the subject of the main clause. That stops the sentence from pointing to the wrong person.

• I made a shopping list while checking the cupboard. I checked the cupboard, and I made the list.

The full version is while I was checking the cupboard. You can also put the short clause first: While checking the cupboard, I made a shopping list. If two different people are involved, keep the subject in the while-clause.

• I made a shopping list while my flatmate checked the cupboard.

Shortening is not limited to -ing forms. You can also see while with an adjective or a phrase after leaving out a subject and be, as in while still at work. Make sure the shortened words describe the right person or thing.

• I checked the figures while still at work. I was still at work when I checked them.

While need not always have a full clause after it, so a rule such as "while must always have a subject and a verb" is too broad.

Nearby words and other meanings

Since gives a starting point, not a length. For answers how long; since answers from when. Use I've known our neighbour for seven years or I've known our neighbour since 2019. In the since version, 2019 names the start; it is not a number of years.

In also has time meanings. I'll be away for three weeks gives the length of an absence. I'll leave in three weeks places the departure three weeks from now. After a negative, for and in can overlap: I haven't used this camera for months and I haven't used this camera in months can both fit. Do not mark in wrong in that negative pattern.

When and as can overlap with time-while. When can also point to a single event rather than a continuing background. Use When the lift stopped, I pressed the alarm for a response to that event. Use I pressed the alarm while the lift was moving to place the pressing inside an ongoing situation. These are different relationships, not a claim that when must mean after.

Whilst is another conjunction with the time meaning of while. Cambridge describes it as more formal. You do not need it to build this pattern.

A while is different again: it is a noun phrase meaning a period of time. In Wait here for a while, for introduces the length, and a while names it. The while in while we wait is a conjunction, not that noun.

While can also express contrast, not time, as in My room faces the street, while yours faces the garden. That meaning belongs with Although, though, despite and other contrast links and Connecting ideas within and between sentences, not the time comparison here.

What comes next

The present perfect with just, yet, already, ever, for and since explains for and since with the present perfect. by, until and by the time compares a deadline with an end point, and at, on and in for time covers at, on and in. For more clause links and future time meanings, see when, while, before, after, until and as soon as and Future time clauses: when, as soon as, if and until. Past and perfect participle clauses: invited, having checked develops shorter clauses. Other meanings of for, such as a present for someone or a reason for doing something, are outside this time comparison.