For, during, while, by, until and on time
For two hours, during the film, while I was waiting; by Friday or until Friday; on time or in time.
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These words all talk about time, and they are easy to mix up. For says how long. During says when, with a noun. While says when, with a subject and a verb. By is a deadline: not later than. Until is the end of a period: up to that time. On time means at the planned time, and in time means early enough.
For or during?
For + a period answers How long?: for two hours, for a week, for ages. During + a noun answers When?: something happens at some point in that time, or all through it.
- I waited for two hours.
- We stayed in Rome for a week.
- My phone rang during the film.
- It rained during the night.
- Incorrect: I lived in London during two years.
- Correct: I lived in London for two years.Two years says how long, so use for.
Both can be in one sentence: I slept for two hours during the flight.
During or while?
During goes before a noun. While goes before a subject + verb.
- During the meeting, my phone rang.
- While I was in the meeting, my phone rang.
- Someone stole my bag while I was on the beach.
- Incorrect: Someone called during I was in the shower.
- Correct: Someone called while I was in the shower.After during comes a noun. Before a subject and a verb, use while.
While often goes with the past continuous for the longer action, as on the A2 page about the past simple and the past continuous.
By or until?
Until (or till in speech) means the situation continues up to that time and then stops. By means "not later than": something happens at that time or before it.
- I'll wait until six. (I'll be here from now to six.)
- Please send me the report by Friday. (On Friday or before.)
- The shop is open until eight.
- Incorrect: I'll wait for you by six.
- Correct: I'll wait for you until six.Waiting continues up to six, so use until.
- Incorrect: You need to finish this until the end of the month.
- Correct: You need to finish this by the end of the month.A deadline: at that time or before it, so use by.
Not ... until means that something starts only at that time: The shop doesn't open until ten. (Not before ten.)
By and until in the past
The difference is the same in the past. Until says how long a situation went on. By says that something was finished at that time or before it.
- We waited until midnight, and then we went home.
- By ten o'clock, everyone had left.
- I hadn't heard about it until you told me.
On time or in time?
On time means at the time that was planned: not late. In time means early enough for something, or to do something. Just in time means with very little time left.
- The trains here are always on time.
- The meeting started on time, at nine.
- We got to the cinema in time to see the start.
- I want to be home in time for dinner.
- Incorrect: The trains here are always in time.
- Correct: The trains here are always on time.For keeping to the timetable, use on time.
For or since?
Remember the difference from the page about for and since: for + a period, since + a starting point: for three years, since 2022.