'Since' and 'For' are prepositions of time that are commonly used with the Present Perfect and Present Perfect Continuous tenses. The key to using them correctly is understanding the specific time information each one provides.
For
For is used to describe a duration of time. It tells us how long an action or state has been happening. It's often followed by a quantity of time.
* Structure: for + a duration of time
* Common Durations: two hours, a week, three years, a long time, many centuries.
Examples:
* I have lived here for five years. (The duration is five years.)
* She has been studying for three hours. (The duration is three hours.)
* We have known each other for a long time. (The duration is a long time.)
* He has worked at that company for a decade. (The duration is a decade.)
Since
Since is used to describe a starting point in time. It tells us when an action or state began. It's often followed by a specific time or event in the past.
The Present Perfect is used with since.
* Structure: since + a specific point in time
* Common Starting Points: 2010, last Tuesday, yesterday, I was a child, he left.
Examples:
* I have lived here since 2020. (The starting point is 2020.)
* She has been studying since 9 a.m. (The starting point is 9 a.m.)
* We haven't seen them since last Christmas. (The starting point is last Christmas.)
* He has been famous since he won the competition. (The starting point is a specific event.)
Key Differences at a Glance
| | For | Since |
| Meaning | How long? (duration) | When did it start? (starting point) |
| Followed By | A quantity of time | A specific time or event in the past |
| Examples | for 10 years <br> for two weeks <br> for ages | since 2015 <br> since last month <br> since I was a child |
Common Mistakes
A common mistake is confusing the two. Remember, if you can ask "How long?" the answer is for. If you can ask "Since when?" the answer is since.
* Incorrect: I have worked here since three years.
* Correct: I have worked here for three years. (Duration)
* Incorrect: They have been married for their wedding day.
* Correct: They have been married since their wedding day. (Starting point)
By keeping this distinction in mind, you can easily use for and since to provide clear and accurate time information in your sentences.
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