For or since?

These prepositions are used to indicate that an event, which is true now, has been taking place for a period of time. We have to be careful when we use them though as they cannot be used interchangeably.

For - used with a period of time, when talking about an action in the past that is still true in the present.

This preposition is used with the present perfect tense -

I have + past participle + for + a time period

Let's clarify this with some examples:

I have worked here for 6 months (not since 6 months)

I have lived in the New York for 5 years (not since 5 years)

I haven't drunk coffee for 10 months (not since 10 months)

I have known you for 7 years (not since 7 years)

We have been married for 26 years (not since 26 years)

Since - used with a specified time in the past, when talking about an action in the past that is still true in the present

This preposition is also used with the present perfect tense -

I have + past participle + since + a specified time in the past

Let's clarify this with some examples:

I have worked here since June

I have lived in the New York since 2015

I haven't drunk coffee since February

I have known you since 2003

We have been married since 1994

Top tip:

For - a period of time (5 years)

Since - a specified time (2015)