Grammar
A2–B2
6 min read
Updated 9 June 2026
Quick Answer
For is used with a period of time (for three days, for years, for a long time). Since is used with a point in time (since Monday, since 2010, since I was a child). Both are common with the present perfect tense.
Two of the most frequently confused time words in English are since and for. Both are used with the present perfect, both relate to time, and both can appear in similar-looking sentences. The key is simple once you know it: for answers "how long?" while since answers "from when?".
The Core Rule
| Word | Used with | Answers the question | Example |
|---|
| for | a period / duration of time | How long? | for two hours, for a week, for ages |
| since | a specific point in time | From when? | since 9 o'clock, since last year, since she left |
Using “For” with Durations
For describes how long an action or state has lasted. It is followed by a measurement of time — a number of seconds, minutes, hours, days, weeks, months, or years, or a general length like a long time or ages.
I have lived here for ten years.
She waited for two hours.
We haven't spoken for a long time.
He studied for three months before the exam.
Key Test
If you can replace the time expression with a number (e.g., two hours, six months, three years), use for.
Using “Since” with Starting Points
Since marks the specific point in the past when an action or state began. It is followed by a date, a day, a year, a time, or a clause describing the starting moment.
I have lived here since 2016.
She has worked here since last Monday.
We haven't spoken since the argument.
He has been happy since he got the job.
Key Test
If you can point to a specific moment on a calendar or clock, or describe the starting event, use since.
Since and For with the Present Perfect
Both since and for are most commonly used with the present perfect (have/has + past participle) or the present perfect continuous (have/has been + -ing). This is because both words describe a situation that started in the past and continues to the present.
I have known her for five years. (duration)
I have known her since 2021. (starting point)
They have been waiting for an hour. (duration)
They have been waiting since noon. (starting point)
Can “For” Be Used with Other Tenses?
Yes. For can be used with any tense when describing duration. It is not limited to the present perfect.
She lived in Paris for three years. (past simple — she no longer lives there)
I will be away for a week. (future)
He was sleeping for hours. (past continuous)
Since, on the other hand, is almost always used with a perfect tense, because it describes something that began in the past and is still relevant now.
Common Mistakes to Avoid
I have lived here since ten years.
I have lived here for ten years. (duration, not a point)
She has been here for Monday.
She has been here since Monday. (a specific day)
We haven't met since a long time.
We haven't met for a long time. (a duration)
Since as a Conjunction
When since is followed by a clause (subject + verb), it functions as a conjunction. The verb in the since clause is usually in the past simple, while the main clause uses the present perfect.
Since she moved to London, she has made many friends.
Things have changed a lot since I was a child.
Since the company was founded, it has grown rapidly.
Quick-Reference Summary
| Situation | Use | Example |
|---|
| Number of years/months/days | for | for five years |
| Vague duration (ages, a while, a long time) | for | for ages |
| Specific year or date | since | since 2015 |
| Day of the week or month | since | since Tuesday |
| Named event or moment | since | since the meeting |
| Clause with past event | since | since she left school |
Related Grammar Topics
Understanding since and for is closely connected to the present perfect tense. See also:
Frequently Asked Questions
What is the difference between since and for?
For is used with a period or duration of time — it tells you how long something has lasted: for two hours, for three years, for a long time. Since is used with a specific starting point in time — it tells you from when something has been happening: since Monday, since 2010, since she arrived. Both are commonly used with the present perfect tense.
Do I use since or for with the present perfect?
Both since and for are used with the present perfect. Use for when you specify the length of time: I have studied English for five years. Use since when you specify the starting point: I have studied English since 2019. The choice depends on whether you are expressing a duration (for) or a point of origin (since).
Can I say "since three years"?
No. "Since three years" is incorrect because "three years" is a duration, not a point in time. You should say "for three years." If you want to use since, you need a specific point: "since 2021" or "since three years ago." The phrase "three years ago" works with since because it identifies a specific moment in the past.
Can "for" be used with past simple?
Yes. For can be used with any tense when expressing duration. With the past simple it means the action is now finished: She lived in Rome for two years (but she doesn't live there now). With the present perfect it means the action is still ongoing: She has lived in Rome for two years (and she still does). The tense, not the word "for," signals whether the action is finished or continuing.
Is "since" always used with the present perfect?
Almost always, yes. Since typically requires a perfect tense (present perfect or past perfect) because it describes something that started at a point in the past and has continued up to a reference point. However, in informal speech you sometimes hear since with the simple past: I haven't seen him since he left (present perfect in the main clause; past simple in the since clause). The since clause itself takes the past simple.
How do I use "since" as a conjunction?
When since introduces a clause (subject + verb), it acts as a conjunction. The since clause uses the past simple, while the main clause uses the present perfect: Since she started the new job, she has been much happier. Since we moved house, everything has changed. Note that since can also mean "because" in formal writing: Since you asked, I will explain — this is a different usage unrelated to time.
What words follow "for" in time expressions?
For is followed by a quantity of time: for a second, for minutes, for two hours, for a day, for weeks, for six months, for a year, for decades, for ages, for a long time, for ever. Any expression that measures a span or length of time works with for. If you could answer the question "How long?" with the phrase, for is the right choice.
What words follow "since" in time expressions?
Since is followed by a specific moment or event: since this morning, since 3 o'clock, since Monday, since last week, since January, since 2020, since childhood, since the war, since I was born. Any expression that identifies a point in time rather than a length works with since. You can think of it as marking the starting line on a timeline.
Can "since" and "for" be used with negative sentences?
Yes. Both work in negative sentences with the present perfect: I haven't eaten since breakfast (since — a specific point). I haven't eaten for six hours (for — a duration). Negative constructions with since and for are very common in English and follow exactly the same rules as positive sentences.
What is "for" used for besides time?
For has many uses beyond time. It can express purpose (I bought it for you), reason (famous for its cuisine), exchange (I paid £10 for it), destination (leaving for Paris), support (I'm for the idea), and more. When used with time, for always expresses duration. The time use is one specific meaning among many, but the duration rule is consistent: for + period of time.