1. General Difference Between For and Since
- For is used to talk about the duration (the length of time something continues).
It answers the question “How long?” - Since is used to talk about the starting point of an action or event that continues until now.
It answers the question “From when?”
Examples:
- I have lived in Tokyo for five years.
(This tells us the length of time: five years.) - I have lived in Tokyo since 2020.
(This tells us the starting point: the year 2020.)
2. Using For – Talking About Duration
The word for introduces a period of time. It shows how long something lasts. The duration can be long or short, and it can be expressed in minutes, hours, days, months, years, or even centuries.
Common Time Expressions with For
- Seconds, minutes, hours: for 10 seconds, for 20 minutes, for three hours
- Days, weeks, months: for two days, for four weeks, for six months
- Years, decades, centuries: for five years, for two decades, for centuries
- Other durations: for a long time, for ages, for a short while
Examples with For
- She waited for 30 minutes before the train arrived.
- We studied English for six months.
- He has been asleep for three hours.
- They lived in Paris for a decade.
- I have known her for a long time.
In all these sentences, for shows how long the action lasted or has lasted.
Tense Usage with For
- For can be used with many tenses, not only present perfect.
Examples: - Past Simple: He stayed in London for two weeks.
- Present Perfect: I have studied Japanese for three years.
- Future: We will be in Spain for a month.
This shows that for is more flexible than since because it can describe duration in the past, present, or future.
3. Using Since – Talking About Starting Points
The word since introduces the exact starting point of an action that continues up to the present (or to a specific time in the past or future). It does not describe duration, but rather the moment something began.
Common Time Expressions with Since
- Exact times: since 7 o’clock, since 3:15 p.m.
- Dates: since Monday, since May 1st, since 2010
- Events: since my birthday, since we met, since the war ended
Examples with Since
- She has lived here since 2015.
- I haven’t seen him since last week.
- They have been married since June.
- We have known each other since childhood.
- He has not eaten anything since this morning.
In each case, since identifies the starting point of the action.
Tense Usage with Since
- Since is almost always used with the present perfect tense or the present perfect continuous tense, because these tenses connect the past starting point with the present.
Examples:
- Present Perfect: I have worked here since 2010.
- Present Perfect Continuous: She has been studying English since this morning.
It can also appear with past perfect when the reference point is in the past:
- Past Perfect: He had lived there since 1998, before moving to Canada in 2005.
4. Comparing For and Since
Because for shows duration and since shows starting point, they cannot be swapped. If you change one for the other, the sentence becomes incorrect.
Examples:
- ✅ I have been here for two hours.
- ❌ I have been here since two hours. (incorrect)
- ✅ I have been here since 2 p.m.
- ❌ I have been here for 2 p.m. (incorrect)
Think of it this way:
- For answers “How long?” → for three days, for ten years
- Since answers “Since when?” → since Monday, since 2012
5. Practical Examples in Conversation
Let’s look at real-world examples where both for and since are used.
Dialogue 1
A: How long have you been waiting?
B: I’ve been waiting for 20 minutes.
Dialogue 2
A: When did you move to Tokyo?
B: I moved here in 2018, so I’ve been here since 2018.
Dialogue 3
A: Are you tired?
B: Yes, I’ve been working for eight hours straight, since 9 a.m.
Notice how in Dialogue 3, both for and since can be used together:
- for gives the duration (eight hours).
- since gives the starting point (9 a.m.).
6. Common Mistakes with For and Since
Mistake 1: Using since with a duration
- ❌ I have studied English since five years.
- ✅ I have studied English for five years.
Mistake 2: Using for with a point in time
- ❌ I have studied English for 2018.
- ✅ I have studied English since 2018.
Mistake 3: Forgetting tense agreement
- ❌ I study English since 2015.
- ✅ I have studied English since 2015.
Remember: Since usually requires a present perfect or present perfect continuous tense.
7. Special Notes About For and Since
- Omission of for
In casual English, for is sometimes dropped, especially with expressions like “a long time” or “ages.”
- I haven’t seen her (for) ages.
- Since as a Conjunction
Besides being a time marker, since can also mean “because.”
- Since you are here, let’s start the meeting.
But in this explanation, we focus only on its time meaning.
- Flexible Expressions with For
For can also be used with general terms:
- for ever, for once, for the moment.
These do not always indicate exact time duration but are set phrases in English.
8. Practice Sentences (Fill in the Blank)
Try to decide whether for or since is correct in these sentences:
- She has worked at that company ___ 10 years.
- He has been at the station ___ 3 p.m.
- We stayed in Italy ___ two weeks.
- I have known her ___ childhood.
- They will be away ___ the summer holidays.
Answers:
- for
- since
- for
- since
- for
9. Summary
- For is used to express duration — the length of time an action lasts.
→ I studied English for three years. - Since is used to express the starting point of an action that continues until now.
→ I have studied English since 2018. - For can be used with many tenses (past, present, future).
- Since is mainly used with present perfect or present perfect continuous tenses.
The easiest way to remember:
- For = How long?
- Since = Since when?
10. Conclusion
Mastering for and since is essential for talking about time in English. By remembering the key difference — duration versus starting point — you can avoid common mistakes and make your speech more natural. Practice using both in conversation by thinking about how long you have done something (for) and when you started doing it (since). With enough practice, choosing the right word will become automatic.
