✅ Since
Use since with a starting point: since Monday, since 2020, since I moved here.
✅ For
Use for with a length of time: for two days, for six years, for a long time.
❌ Wrong: I have lived here since three years.
✅ Correct: I have lived here for three years. / I have lived here since 2023.
Since and for both talk about time, but they answer different questions. Since answers “When did it start?” For answers “How long did it last?” That is the simplest way to choose the right word.
Since vs For: The Main Difference
Use since when you give the exact point when something began. That point can be a date, a year, a day, a time, or even a full clause.
✅ I have known her since 2018.
✅ He has worked here since Monday.
✅ We have been friends since we were children.
Use for when you give the amount of time. You are not saying the start point. You are saying the length.
✅ I have known her for six years.
✅ He has worked here for two days.
✅ We have been friends for a long time.
A useful shortcut: since points to the beginning. for measures the duration.
Use Since for a Starting Point
Since tells the reader when an action, state, or situation started. The action may still be true now, especially when used with the present perfect.
- since yesterday
- since last week
- since January
- since 9 a.m.
- since 2020
- since I arrived
In each phrase, since introduces a clear starting point. It does not show the full length by itself.
Since With Dates and Years
Use since before a calendar point.
✅ She has lived in London since 2021.
✅ I have played guitar since June.
Since With Events
Use since before the event that started the time period.
✅ He has been happier since he changed jobs.
✅ The room has been quiet since the meeting ended.
Use For for a Length of Time
For tells the reader how long something continues, continued, or will continue. It works with seconds, minutes, hours, days, months, years, and general time expressions.
In these examples, for gives a duration. It does not name the exact starting point.
✅ They stayed at the hotel for three nights.
✅ I studied English for two hours.
✅ She has waited for a long time.
Simple Rule: Starting Point or Duration?
| Question | Use | Example |
|---|---|---|
| When did it start? | Since | I have lived here since 2020. |
| How long has it lasted? | For | I have lived here for four years. |
| What was the first moment? | Since | She has been awake since 6 a.m. |
| What is the time length? | For | She has been awake for five hours. |
Since and For With Present Perfect
Since and for often appear with the present perfect: have/has + past participle. This structure connects the past to the present.
Present Perfect With Since
✅ I have worked here since March.
✅ She has known him since college.
✅ We have lived here since we got married.
Present Perfect With For
✅ I have worked here for eight months.
✅ She has known him for many years.
✅ We have lived here for a decade.
Notice the difference. Since March gives the starting point. For eight months gives the total time. Both can describe the same situation, just from a different angle.
Since and For With Past Simple
For can be used naturally with the past simple when the action is finished.
✅ We stayed in Rome for five days.
✅ He worked there for two years.
✅ I waited outside for twenty minutes.
Since can also appear with past-time meaning, but it usually connects one past moment to a later moment. In everyday grammar questions, learners most often use since with perfect tenses.
✅ I had not seen her since 2019.
✅ He had felt nervous since the interview.
✅ They had been friends since childhood.
Common Mistakes With Since and For
The most common mistake is using since before a duration. A duration tells how long, so it needs for.
| Incorrect | Correct | Why? |
|---|---|---|
| I have lived here since three years. | I have lived here for three years. | Three years is a duration. |
| She has studied English since two months. | She has studied English for two months. | Two months tells how long. |
| We have been waiting since an hour. | We have been waiting for an hour. | An hour is a length of time. |
| He has worked here for 2020. | He has worked here since 2020. | 2020 is a starting point. |
| I have known her for last summer. | I have known her since last summer. | Last summer points to when it began. |
Ask yourself one short question: Can I count the time length? If yes, use for. If you are naming the first point in time, use since.
Since With a Clause
Since can introduce a full clause. A clause has a subject and a verb. This is useful when the starting point is not just a date or time, but an event.
✅ I have felt better since I started exercising.
✅ She has been busy since she joined the new team.
✅ The house has been quieter since the guests left.
In these sentences, the clause after since tells us when the situation began. It does not tell us the exact duration.
For With Exact and General Time Periods
For works with both exact and general time periods. The time can be very precise, or it can be broad and natural.
Exact Time Periods
- for 30 seconds
- for two weeks
- for six months
- for ten years
General Time Periods
- for a while
- for ages
- for a long time
- for most of my life
Both types are correct. For two weeks is exact. For a while is general. The grammar is the same because both phrases describe duration.
Can Since and For Mean the Same Thing?
They can describe the same real-life situation, but the focus changes. One sentence gives the starting point. The other gives the length of time.
✅ I have lived in this city since 2020.
✅ I have lived in this city for four years.
Both sentences may be true. The first sentence answers “When did you start living here?” The second answers “How long have you lived here?”
Since vs For in Negative Sentences
The same rule works in negative sentences. Use since for the starting point. Use for for the length of time.
✅ I haven’t seen him since Friday.
✅ I haven’t seen him for three days.
✅ She hasn’t called since last week.
✅ She hasn’t called for a week.
Be careful with meaning. I haven’t eaten since breakfast means breakfast was the last time I ate. I haven’t eaten for six hours tells the length of time without food.
Since vs For in Questions
Questions make the difference even clearer. Use since when to ask about the starting point. Use how long to ask about duration.
| Question Type | Example Question | Natural Answer |
|---|---|---|
| Starting point | Since when have you lived here? | Since 2022. |
| Duration | How long have you lived here? | For two years. |
| Starting point | Since when has she worked there? | Since January. |
| Duration | How long has she worked there? | For several months. |
Since, For, From, and During
Since and for are easy to confuse with from and during. Each word has its own job.
| Word | Use It For | Example |
|---|---|---|
| Since | A starting point that connects to a later time | I have worked here since 2021. |
| For | A duration | I worked there for three years. |
| From | The start of a range | The shop is open from 9 a.m. to 5 p.m. |
| During | Something that happens inside a period | She took notes during the meeting. |
Do not use during with a length of time. Say for two hours, not during two hours, when you mean duration.
Mini Practice: Choose Since or For
Try choosing the word before reading the answer. Is the phrase a starting point or a duration?
- I have had this phone _____ last December.
- They have been married _____ ten years.
- She has worked from home _____ the office closed.
- We waited _____ forty minutes.
- He has not visited us _____ 2022.
Answers
- since last December
- for ten years
- since the office closed
- for forty minutes
- since 2022
How to Remember Since and For
Think of since as a pin on a timeline. It marks the place where something began. Think of for as a ruler. It measures the time from one point to another.
A Simple Memory Trick
Since = start. For = length. If the phrase tells when something began, choose since. If it tells how long it lasted, choose for.
More Correct Examples
Use Since
- I have been awake since sunrise.
- She has lived alone since college.
- We have known each other since 2015.
- He has felt tired since the trip.
- The store has been open since 8 a.m.
Use For
- I have been awake for six hours.
- She lived alone for a year.
- We have known each other for nine years.
- He slept for most of the trip.
- The store was open for eight hours.
Frequently Asked Questions About Since and For
Is It “Since Two Years” or “For Two Years”?
The correct phrase is for two years. Two years is a duration, so it needs for. You can say since 2022 if you want to give the starting year.
Is “Since Yesterday” Correct?
Yes. Since yesterday is correct because yesterday is a starting point. Example: I have felt tired since yesterday.
Can I Use For With Present Perfect?
Yes. For is very common with the present perfect when you talk about duration. Example: I have lived here for five years.
Can I Use Since With a Full Sentence?
Yes. Since can come before a clause. Example: She has been more confident since she started practicing every day.
What Is the Biggest Since vs For Mistake?
The biggest mistake is using since with a duration. Say for three weeks, for ten minutes, and for many years. Use since with starting points like Monday, 2020, or I arrived.
