Since, For, and Ago: Talking About Time Without Confusion

Since, for and ago all answer questions about time, but each answers a different question.

Since = from what starting point?

Use since before the point when a situation began: since Monday, since 2021, since breakfast, since I moved here.

I have lived here since 2021.

For = for how long?

Use for before a period or duration: for two hours, for six months, for a long time.

I have lived here for three years.

Ago = how long before now?

Use ago after a length of time to locate a finished event in the past. It normally goes with Past Simple.

I moved here three years ago.
She called ten minutes ago.

Compare the three patterns

I started this job two years ago.
I have worked here for two years.
I have worked here since September 2024.

All three can describe the same situation from different angles.

Typical mistakes

I live here since three years. → I have lived here for three years.

I have met him two days ago. → I met him two days ago.

I’ve been here since five hours. → I’ve been here for five hours.

Practice

1. We’ve known each other ___ 2019.
2. I’ve been waiting ___ twenty minutes.
3. He left half an hour ___.
4. She has worked remotely ___ last summer.

Answers: since; for; ago; since.

Memory shortcut: since = starting point; for = duration; ago = finished distance back from now.