Since vs. For
Since and for can both locate a situation in time, but they answer different questions. Since introduces the starting point from which a situation continues; for introduces a duration or period of time.
Use since with a starting point and for with a duration: since 2020, for three years.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| a starting point in time | since + starting point | Use “since.” |
| a length or duration of time | for + duration | Use “for.” |
| a non-temporal meaning such as cause/reason | since in another documented sense | Do not apply the time rule mechanically outside temporal use. |
Quick tests
Meaning / construction test
Does the time expression identify when the period began?
If yes: Use “since.”
If no: If it states how long the period lasts, use “for.”
Caveat: The starting-point/duration contrast applies to temporal use; “since” has other meanings.
Examples
She has lived here since 2020.
“2020” is the starting point.
She has lived here for six years.
“Six years” is the duration.
We have been waiting since noon.
“Noon” identifies when the waiting began.
Further guidance
Tense Boundary
The tense depends on the whole sentence; the since/for distinction itself is point versus period.
Time Boundary
Do not use since with a duration such as three hours; use for for the length of time.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- For or since? (opens in a new tab)Cambridge Dictionary · For with periods of time and since with starting points