We use since & for to say how long something has been happening. Look at these sentences.
He has been in China since May.
He has been in China for six months.

We use since when we talk about when something started.
since yesterday
since 1998
since 10pm

We use for to talk about the length of time (how long).
for 12 hours
for 100 years
for a few minutes

Look at these sentences.
I've been working here since November 2001.
She's been playing baseball since she was 10.
They've been married since 1955.

I've been waiting for a bus for 50 minutes.
She'll be on the airplane for 10 hours.
I've been learning Spanish for a long time.

Put in the missing word.

1. She has been on a diet January.
2. He has been a hairdresser 20 years.
3. She'll be studying medicine 6 years.
4. I haven't been to the doctor 1999.
5. Do you mind waiting a few minutes?
6. She's gone shopping. She won't be home hours.

Go back to Grammar Book.