Telling time in English can be tricky. Two little words—since and for—cause endless confusion, even for advanced learners. Here’s the quick fix: for talks about duration; since talks about a starting point. That’s it.
The Rule in Plain English
Use for when you want to say how long something has been happening. Use since when you want to say when it started.
- For + a period of time (two hours, three years, a decade)
- Since + a specific point (Monday, 9 AM, 2020)
Examples:
-
I’ve lived here for three years. (duration)
-
I’ve lived here since 2022. (starting point)
-
She’s been asleep for six hours.
-
She’s been asleep since noon.
Notice the pattern? Both sentences use the present perfect (or present perfect continuous), but the time expression changes.
The Sneaky Mistake Learners Make
The most common error is mixing them up. A student might say “I’ve been working here since two months” – but that’s wrong. “Two months” is a duration, not a starting point. It should be “for two months.”
Another trap: thinking “since” always means a date or a clock time. It can also be an event: “I’ve been happy since I met you.” The event itself is the starting point.
Quick Reference Table
Here’s a simple visual way to remember.
For
Duration
a minute, two hours, weeks, ages, a long time, ten years
Since
Starting point
2 o’clock, Monday, March, 2015, childhood, last winter
If you can count the length (e.g., “two hours”), use for. If you can point to a moment or event (e.g., “2 o’clock”), use since.
A Little Trick to Never Forget
Think of for as describing a fence around a period. You measure the space inside the fence.
Think of since as an arrow that starts at one point and keeps going forward.
- For = length of time → ask “How long?”
- Since = starting time → ask “When did it begin?”
Practice: Choose the Right Word
Try these two sentences:
- I’ve known her ___ 2019.
- I’ve known her ___ five years.
Answers: 1. since 2. for
If you got them right, you’ve mastered it. If not, re‑read the table above—it sticks after a few tries.
Ready to Test Your English?
The difference between since and for is just one piece of the puzzle. Knowing when to use the right word makes your English sound natural and confident.
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