If you have ever hesitated before writing since or for in a sentence about time, you are not alone. The direct answer is this: use for to talk about a duration or length of time, and use since to talk about a specific starting point in time. For answers the question “how long?” and since answers the question “from when?”. This guide will give you clear rules, natural examples, common mistakes to avoid, and practice to help you use both words correctly in writing, email, and conversation.
Quick Answer: Since vs. For
Here is the simplest way to decide which word to use:
- For + a period of time (e.g., two hours, three days, a year, a long time).
- Since + a specific point in time (e.g., Monday, 2020, 9 AM, last summer, I moved here).
Think of for as measuring the distance between two points, and since as naming the starting point. If you can replace the time expression with “how long,” use for. If you can replace it with “from when,” use since.
Detailed Explanation of Since and For
Using For (Duration)
We use for when we want to say how long something lasts or lasted. It is always followed by a noun phrase that expresses a length of time. This works with all tenses: past, present, and future.
Examples:
- I have lived here for five years.
- She studied French for three months.
- We will be on vacation for two weeks.
- He has been asleep for a short while.
Common time expressions with for: a minute, an hour, two days, a week, a month, several years, a decade, a long time, ages, a while.
Using Since (Starting Point)
We use since to mark the moment when an action or situation began. It is most common with perfect tenses (present perfect, past perfect, present perfect continuous). Since is followed by a specific time, date, event, or clause.
Examples:
- I have lived here since 2019.
- She has been studying French since January.
- They have not spoken since the party.
- He has been feeling better since he started the new medicine.
Common time expressions with since: Monday, 8 o’clock, last week, 2015, yesterday, I was a child, the meeting ended.
Formal and Informal Tone
Both since and for are neutral and can be used in any register. In formal writing or professional emails, you will often see them with present perfect or past perfect tenses. In casual conversation, people sometimes drop the word for in short answers (e.g., “I waited two hours”), but this is not correct in careful writing. Stick to using for in formal contexts.
Email and Conversation Context
In emails, since is useful when you need to refer to a previous event or date. For example: “Since our last meeting, we have made significant progress.” In conversation, for is very common when talking about experience: “I have known her for ten years.” Both words are essential for clear time references.
Comparison Table: Since vs. For
| Feature | Since | For |
|---|---|---|
| Meaning | From a starting point | Duration or length of time |
| Question it answers | From when? | How long? |
| Followed by | A specific point (date, event, time) | A period of time (hours, years, minutes) |
| Common tenses | Perfect tenses (present perfect, past perfect) | All tenses (past, present, future) |
| Example | I have worked here since 2020. | I have worked here for three years. |
| Can it start a sentence? | Yes (e.g., Since Monday, I have been busy.) | Yes, but less common (e.g., For two days, it rained.) |
Natural Examples in Context
Read these examples to see how since and for sound in real situations.
- Work email: “I have been with the company for six years. Since the new manager arrived, our team has changed a lot.”
- Casual conversation: “I haven’t seen you for ages! What have you been up to since last summer?”
- Writing a diary: “I have been feeling tired for a few days. I think it started since I stayed up late on Friday.”
- Travel story: “We have been traveling for three weeks. Since we left Tokyo, we have visited five cities.”
- Study situation: “She has been learning guitar for two years. She has improved a lot since her first lesson.”
Common Mistakes with Since and For
Mistake 1: Using “since” with a duration
Incorrect: I have been waiting since three hours.
Correct: I have been waiting for three hours.
Why: “Three hours” is a period of time, not a starting point.
Mistake 2: Using “for” with a specific point
Incorrect: She has been a teacher for 2015.
Correct: She has been a teacher since 2015.
Why: “2015” is a specific year, a starting point.
Mistake 3: Forgetting the tense change with “since”
Incorrect: I am living here since last year.
Correct: I have been living here since last year.
Why: Since usually requires a perfect tense (present perfect or present perfect continuous) to show the action started in the past and continues.
Mistake 4: Using “since” to mean “because” in time contexts
Incorrect: Since I was late, I missed the bus. (This is correct if you mean “because,” but it can be confusing.)
Better: I have been waiting since 8 AM. (Here, since clearly means a starting point.)
Note: Since can also mean “because,” but in this guide we focus on time. Be careful not to mix the two meanings in a single sentence.
Better Alternatives and When to Use Them
Sometimes you can replace for or since with other expressions to add variety or clarity.
- Instead of “for a long time”: You can say “for ages,” “for a while,” or “for an extended period.” Example: “I have been waiting for ages.”
- Instead of “since last week”: You can say “from last week onward,” “starting last week,” or “after last week.” Example: “Starting last week, the schedule changed.”
- When you want to emphasize the duration without “for”: Use “over” or “during.” Example: “Over the past three years, we have grown.”
- When you want to emphasize the starting point without “since”: Use “from” or “as of.” Example: “From 2021, I have worked remotely.”
When to use it: Use for and since as your default for clear time references. Use alternatives only when you want to avoid repetition or when the context calls for a more formal or precise expression.
Mini Practice: 4 Questions with Answers
Test your understanding. Fill in the blank with since or for. Answers are below.
- I have known my best friend __________ we were in kindergarten.
- They have been married __________ 25 years.
- She has not eaten anything __________ this morning.
- We have been working on this project __________ three months.
Answers:
- since (specific event: when we were in kindergarten)
- for (duration: 25 years)
- since (specific time: this morning)
- for (duration: three months)
Frequently Asked Questions (FAQ)
1. Can I use “since” with the past simple tense?
Yes, but it is less common. You can say “Since then, I changed my mind.” However, the present perfect is more natural: “Since then, I have changed my mind.” In everyday English, you will hear both, but the present perfect is preferred in careful writing.
2. Is it ever correct to say “for since”?
No. Never use “for since” together. They are separate words with different meanings. If you need to express both duration and a starting point, use two clauses: “I have worked here for five years, since 2019.”
3. What is the difference between “since” and “from” in time expressions?
Since is used with perfect tenses to show an action that continues to the present. From is used with any tense to show a starting point, but it does not imply continuation. Example: “I work from 9 AM to 5 PM” (no continuation implied). “I have worked here since 9 AM” (implies I am still working).
4. Can I start a sentence with “for”?
Yes, but it is less common and can sound formal or literary. Example: “For many years, she lived abroad.” In everyday conversation, it is more natural to say “She lived abroad for many years.” Starting with for is fine in writing, but use it sparingly.
For more help with similar word pairs, visit our Grammar Word Differences section. If you have a question about a specific usage, check our FAQ page or contact us. We also have guides on Usage Confusions and Beginner Comparison Guides to support your learning.
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