GRAMMAR : Present Perfect

Present perfect

We use the present perfect:

• for something that started in the past and continues in the present:

They've been married for nearly 50 years.
She has lived in Liverpool all her life.

• when we are talking about our experience up to the present:

I've seen that film before.
I've played the guitar ever since I was a teenager.
He has written three books and he is working on another

We normally use the present perfect continuous to emphasise that something is still continuing in the present:

It's been raining for hours.
I'm tired out. I've been working all day.

For/since

The words for and since are used in sentences where the speaker wants to talk about something that started in the past and continues into the present.
For is used when specifying the amount of time (how long):

• I've had this watch for more than 40 years.
• I've only known her for a few weeks.
• He's been here for 6 months and still can't speak a word of German.
• She's been smoking for a long time. No wonder she coughs so much!

Since is used when specifying the starting point:

• I've had this watch since 1965.
• I've only known her since the beginning of last week.
• He's been here since April and he still can't speak a word of German.
• She's been smoking since she started grade 5. No wonder she coughs so much!

Note: The present perfect or present perfect continuous are needed in such sentences. It is wrong to say:

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 http://esl.fis.edu/grammar/multi/since.htm