Since or for? It’s simpler than it feels
“Since” and “for” cause more quiet confusion than almost any other pair in English, and it’s a shame, because the rule behind them is genuinely simple. Both words talk about time stretching up to now, which is why they get mixed up. The difference is what kind of time information follows them. Get that one distinction clear and you’ll never guess again.
Here’s the whole rule: use “for” with a length of time, and “since” with a starting point. “For” answers “how long?” — for three years, for two hours, for a few minutes, for ages. It measures the duration, the size of the gap. “Since” answers “starting when?” — since 2018, since Monday, since I was a child, since breakfast. It names the exact moment the clock started ticking. So “for three years” tells you the length; “since 2020” tells you the start. Try it with any time expression: if you can imagine it on a calendar or clock as a single point, use “since”. If it’s a stretch you could measure with a stopwatch, use “for”.
There’s a second half to this, and it’s about tense. Because both words describe something that began in the past and continues to now, they naturally pair with the perfect tenses — usually the present perfect (“I have lived here for ten years”) or the present perfect continuous (“I have been working here since 2020”). This is where a very common mistake creeps in. In many languages you’d use a simple present here — something like “I am working here since 2020” — but English doesn’t allow that. When the action started in the past and is still going, English wants “have been + -ing”. So it’s “I have been studying English for three years”, not “I am studying English since three years”. Two rules, then: match the word to the type of time (duration or point), and reach for the present perfect when the situation runs from past to present. Master both and this topic is done.
The answers, explained
1. “I have been studying English for three years.” Three years is a length of time — a duration — so it takes for. The tempting choice is since, but “since” needs a starting point like “since 2021”, not a span. Ask yourself: is “three years” a point on a calendar or a measured stretch? It’s a stretch, so for.
2. “She has lived in Mumbai since 2018.” The year 2018 is a specific point in time — the moment she moved — so it takes since. “For” is the trap here, but “for 2018” makes no sense because a single year is a starting point, not a duration. If you wanted “for”, you’d have to say “for six years”.
3. “I have been working here since 2020” is the grammatically correct sentence. The action started in the past and continues now, so English requires the present perfect continuous: “have been working”. “I am working here since 2020” uses the simple present, which is the classic mistake — natural in some languages but wrong in English. “I worked here since 2020” uses the past simple, which cuts the action off in the past. “I have working” is missing the “been”.
4. “We haven’t spoken since last Sunday.” “Last Sunday” is a specific point — the last time you spoke — so it takes since. “For” is the distractor, but “for last Sunday” isn’t a duration. A quick test: “since last Sunday” answers “starting when?”, which confirms since.
5. “He has been waiting for two hours.” Two hours is a duration, a measured length of time, so it takes for. “Since” is the tempting wrong option, but you’d only use it with a start point like “since two o’clock”. Two hours on a stopwatch = duration = for.
Quick rules to remember
Two rules carry the whole topic. First, for goes with a length of time (for three years, for two hours) and since goes with a starting point (since 2018, since Monday, since I was young). A quick self-test: if the time word is a point you could mark on a calendar or clock, use since; if it’s a stretch you could measure, use for. Second, because both describe a situation running from the past up to now, pair them with the present perfect or present perfect continuous — “have lived”, “have been working” — never the simple present. The single biggest mistake is “I am living here since 2019”; the fix is always “I have been living here since 2019”.
If you’d like one habit to build this week, make it this: every time you talk about how long something has been going on, pause and ask yourself “point or span?” That half-second check is all it takes. “Since Monday” — that’s a point, so “since” is right. “For five days” — that’s a span, so “for” is right. Do this consciously a dozen times and it becomes automatic. And keep an ear out for the tense too: the moment you’re describing something that started earlier and is still true now, let “have been” lead the way. Point or span, and past-to-now needs the perfect — those two little checks will carry you through almost every sentence you’ll ever need.
Frequently asked questions
What’s the easy way to choose between “since” and “for”?
Ask what follows. If it’s a length of time (three years, two hours, ages), use “for”. If it’s a starting point (2018, Monday, this morning), use “since”. Point in time = since; span of time = for.
Why is “I am living here since 2020” wrong?
Because the situation started in the past and continues now, English needs the present perfect continuous, not the simple present. Say “I have been living here since 2020.” The simple present can’t reach back to a past starting point.
Can I use “since” with a duration like “since three years”?
No. “Since” only works with a starting point, so “since three years” is wrong. You’d say “for three years” (duration) or “since 2021” (starting point).
Do “since” and “for” always need the present perfect?
When you mean something running from the past up to now, yes — use the present perfect or present perfect continuous. “For” can appear with other tenses too (“I’ll be there for an hour”), but in this since/for-with-duration context, the perfect tenses are what you want.