We use for and since to say how long something has been happening.
We use for + a period of time:
- We’ve been waiting for two hours
- Sally has been working here for six months. (not since six months)
- I haven’t seen Tom for three days.
We use since + the start of a period:
- We’ve been waiting since 8 o’clock
- Sally has been working here since April. (= from April until now)
- I haven’t seen Tom since Monday.
We oft en leave out for (but not usually in negative sentences):
- They’ve been married for ten years. or They’ve been married ten years.
- They haven’t had a holiday for ten years. (you need for)
You can use in instead of for in negative sentences (I haven’t … etc.):
- They haven’t had a holiday in ten years. (= for ten years)
We do not use for + all … (all day / all my life etc.):
Compare when … ? (+ past simple) and how long … ? (+ present perfect):
a: When did it start raining?
b: It started raining an hour ago / at 1 o’clock.
a: How long has it been raining?
b: It’s been raining for an hour / since 1 o’clock.
a: When did Joe and Kate first meet?
b: They first met
a: How long have they known each other? b: They’ve known each other a long time ago. when they were at school. ⎧ ⎨ ⎩ for a long time. since they were at school.
- It’s two years since I last saw Joe. or It’s been two years since … (= I haven’t seen Joe for two years)
- It’s ages since we went to the cinema. or It’s been ages since … (= We haven’t been to the cinema for ages)
- How long is it since Mrs Hill died? or How long has it been since … (= when did she die?)
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