Use since to name when a period began, and for to say how long it lasted. For example, “I’ve worked here since 2022” gives the starting point; “I’ve worked here for four years” gives the duration.
Compare the time expressions
| Use | What follows | Example |
|---|---|---|
| since | A starting point: a date, time, or event | We’ve been friends since school. |
| for | A length of time | We’ve been friends for ten years. |
The same distinction works with other tenses:
- Since: She had been waiting since 8 a.m. when the office opened.
- For: She had been waiting for an hour when the office opened.
A starting point can be a phrase such as last summer, Monday, or I moved here. After since, a full clause usually describes the event that marks the start: “I’ve felt better since I changed my routine.” The clause is commonly in the past simple; the main clause often uses the present perfect when the situation continues up to now.
Which tense should you use?
For a situation that began in the past and is still true, the present perfect is common with both words:
- “They’ve lived in Bristol since 2021.”
- “They’ve lived in Bristol for five years.”
The present perfect continuous is also natural for ongoing activities: “I’ve been studying for three hours” or “I’ve been studying since lunchtime.” The simple form can be more natural with verbs such as know and own: “I’ve known Sam for years.”
If the situation is finished, use a past tense: “We stayed for a week and then went home.” Since can also appear with past perfect for a period leading up to a past moment, as in the earlier waiting example.
An important exception: “since” can mean “because”
Since does not always refer to time. It can introduce a reason: “Since the roads are icy, we’ll take the train.” Here, it means because, so it is not interchangeable with for as a duration marker. Context makes the meaning clear.
Also, for has other uses, such as expressing purpose (“This tool is for cutting wood”). The time rule applies when for describes a duration.
Quick check
Check your understanding
Maya has worked at the clinic March 2022. (since/for)
We waited forty minutes before the doors opened. (since/for)
I’ve had this coat I was a student. (since/for)
By noon, the team had been working on the repair six hours. (since/for)
Answers and explanations
since
March 2022 is the starting point.
for
Forty minutes is a duration.
since
“I was a student” names the event or period when the situation began.
for
Six hours is the length of time leading up to noon.
