These prepositions are very commonly used with the present perfect continuous tense. Note that since is used to say when something started. For is used to say how long it has lasted.

It has been raining since morning. (NOT It has been raining for morning.)

It has been raining for two hours. (NOT It has been raining since two hours.)

I have been waiting since yesterday.

I have been waiting for ten hours.

Exercise

Complete the following sentences using appropriate present perfect continuous tense forms of the verb given in the brackets. The second sentence in each sentence has to be filled in with since or for.

1. He ……………………………………… (work) on that computer ……………………………………… he came here.

2. She ………………………………….. (learn) the piano ……………………………. two months.

3. The men …………………………………………… (work) on this project …………………………………… January.

4. That boy …………………………………………… (watch) TV …………………………….. hours.

5. Ram ………………………………………….. (try) to fix the machine ………………………………………… over two hours.

Answers

1. He has been working on that computer since he came here.

2. She has been learning the piano for two hours.

3. The men have been working on this project since January.

4. That boy has been watching TV for hours.

5. Ram has been trying to fix the machine for over two hours.