Agnes Leyen asks:
Could you please tell me the difference (in use) between because, as, since and for. I think it's very confusing.
The present perfect is often used with since and for to denote periods of time up to the present. (Note that we do not use present perfect with expressions that refer to a time period that has finished, i.e. 'last week' or 'the day before yesterday'. Here the simple past is used: 'I went to the cinema three times last week.')
If you use since with the present perfect or present perfect continuous, you are signalling when something started. If you use for, you are signalling how long something has been going on. Compare:
- 'She has been living in Holland since the summer of 1992.'
- 'She has been living in Holland for the last nine years.'
That is one use of since and for.
But since and for can also be used in a similar way to as and because to give the reason for an action or a situation. However, there are important differences between them.