Grammatically speaking, For and Since are both prepositions which can be used in a sentence to express a specific time or period of time depending on the context.
Many believe these prepositions can be used interchangeably but as a matter of fact, that’s not true.
In fact, this is one of the common English errors I’ve seen people commit while expressing themselves on social media websites.
So, what’s the difference between For and Since and how do you use them correctly while talking about time?
Let’s some examples:
Incorrect: I haven’t seen him for last week.
Correct: I haven’t seen him since last week.
Incorrect: She has been suffering from fever since past two weeks.
Correct: She has been suffering from fever for past two weeks.
Since – a Specific Point of Time
You use Since when you talk about a specific point of time in the past around which an event took place. In Example #1 above, “Last Week” is the specific point of time around which the person was last seen. Remember Whatsapp?
Some more examples:
I’ve been missing you since you were gone.
She’s been feeling a bit dizzy since yesterday.
Have you been behaving this way since childhood?
He’s been much better since he quit smoking.
I’ve never liked her since the first time I saw her.
If you pay attention to the underlined phrases in the examples above, you will realize they are actually a specific of time and not a length or period of time.
Important: Note that we use “Perfect Progressive” tense in all of the above examples. That’s because we mean to talk about something which has been occurring from a specific point of time and hasn’t actually stopped happening as we speak.
Therefore, it’s imperative to use this tense every time you use Since to talk about a period of time.
For – a Period of Time in the Past
You use For when you want to talk about a period of time or length of time in the past from which an event has taken place. In Example #2 above, “Past two weeks” is the period of time for which the person has been suffering.
Some more examples:
India hasn’t conceded a boundary for the last ten overs. (in Cricket)
I’ve been meaning to tell you the truth for the past six months!
The Government has been fooling its people for the past three years.
As you can see, the underlined parts in the above examples indicate a period of time, as against a specific point of time.
Important: Note that we use a “Perfect Progressive” tense in all of the examples above. This is because we talk about an event which has been happening for a period of time and it hasn’t stopped occurring yet.
How to Avoid Mistakes while using For vs Since
The trick is to understand what a particular phrase actually means before using the right preposition.
There are many situations which may confuse some learners especially those who don’t use English as their first language.
For example, can you say which of the sentences below is correct?
I’ve been working on this task since a long time.
I’ve been working on this task for a long time.
Well, the second example is the right answer. However, if Google it, you will see this actually confuses many learners.
The reason is some “a long time” may appear like a specific point of time to some while many agree it’s only a period of time in the strict sense.
Even as some users try to use “a long time ago” to mean a specific point of time. For example:
I’ve been living here since a long time ago.
However, it’s still not acceptable in Standard English because the point of time is not very specific here. Unless you specifically want to be secretive about the specific date, you should use for example, since 2010 (date) or last year to denote the specific time.
The good news is you can alter the sentence structure and use both Since and For as per your convenience depending on the message you want to send.
Example #1: I’ve been standing in line for the past two hours.
Example #2: I’ve been standing in line since it was very cold in the morning and ticket counter wasn’t open.
As you can see the second sentence makes a very strong argument.
Recommended Reading: Past Year vs Last Year: Which One is Correct?