Since, For, Ago, Before

Since, for, ago and before

Since, when used with the present perfect tense, means from a point or period of time in the past up to now.

• I have lived here since my childhood.
• I haven’t seen him since last week.
• India has made tremendous progress since the dawn of independence.

For

For, when used with the present perfect tense, refers to a period of time up to now.

• We have lived here for twelve years.
• He has been working here for three years now.
• The strike has continued for two weeks.

Ago

Ago is used when you date back from now to a point of time in the past.

• It was two years ago that I first met Alice.
• I saw him two months ago.

Before

Before is used when you date back from any point of time in the past or future.

• The roof must be repaired before the rain starts.
• I think I have seen him before.