I’m sure you’re familiar with the three words above. They’re all very commonly used in English.
But did you know that they have more than one meaning? Do you know all their different meanings?
First, let’s talk about the most common ones.
All three words above are used to talk about time.
Let’s talk about “for” and “since.”
“For” and “since” are Prepositions. You can see these two words most often together with the Present Perfect Tense (Have P.P.) This is because they both talk about duration. A duration means the period of time that an action is done or an event happens.
I read a book for a while.
I’ve known her since high school.
But as you might notice, even though they both talk about a time span (period), they’re not exactly the same.
Why? What’s the difference between them?
For + the duration
Since + the starting point of the duration
This is why you can either say:
I’ve known how to drive for 6 years.
I’ve known how to drive since 2007.
And they would have very similar meanings.
If you want to know which one of them to use, it will depend largely on whether you want to talk about (A) how long you have been doing something or (B) when you started doing something.
So, choose your Time expression appropriately.
Here are some more examples:
I’ve been a big fan of Harry Potter for 15 years.
I’ve been a big fan of Harry Potter since 1998.
I’ve had my pet Shasha for 8 months.
I’ve had my pet Shasha since May last year.
“For” talks about a long stretch of time, while “since” talks about an exact point in time.
The last difference between them is: when you use “since,” the period of time must continue until the present. “For” isn’t like this.
I worked in that company for 10 years. (finished) = Ok
I have worked in that company for 5 years. (until now) = Ok
I worked in that company since 2003. (finished) = X
I have worked in that company since 2008. (until now) = Ok
So, I hope you don’t mix them up when you use them.
Since + Ago?
Some people have the habit of combining the words “since” and “ago.” This way:
I’ve been studying English since 6 years ago.
I’ve been studying English for 6 years.
There’s been quite a debate about whether a combination of “since” and “ago” is acceptable or not. Some grammar books say that we should stick to what’s direct and simple: ex. for 6 years.
But still, you can hear some people using the combination mentioned above.
My advice to my readers, who are non-native ESL learners, is to practice and be comfortable with using the original structures first:
For 6 years
At the same time, practice yourself with using “ago” with only the Past Simple and not the Present Perfect. Because if you don't, it could give you a lot of problems in the future:
I came here two minutes ago. = Ok
I’ve come here two minutes ago. = X
The two words that we discussed above are both Prepositions, which is why they are followed by Nouns. Right now we are going to start talking about “as,” which is often a Conjunction.
Now, what is a Conjunction?
A Conjunction is a type of word that is used to combine sentences and clauses. So,
Preposition + Noun
Conjunction + S + V
So, “as” will be followed by more words. (Not a single Noun)
The phone rang as I was leaving.
He called as we were having dinner.
I saw her as I was entering the bar.
As time passed, he felt more and more bored.
As you can see from our examples above, the Conjunction “as” is used with the same meaning as “when” or “while.”
Note: “As” has so many other meanings but we will not talk about all of them here.
After everything that we talked about, you will be surprised to know that, in spite of their differences, all the three words – “as,” “for,” and “since” – also have the meaning of “because.”
It’s true. The reason is that “for” and “since” are sometimes also used as Conjunctions:
I skipped my lesson today, for I had felt a fever coming on.
I don’t need to go there today since I already finished all my tasks.
Since you didn’t tell her exactly what to do, she’ll just do whatever she wants.
Don’t be confused. Now, the meaning of “since” and “for” is not about time. Now, both of them mean “because.”
Note: You should remember though that when we use “for” in this form, it becomes formal.
On the other hand, the word “as” will still remain a Conjunction, but it will have another meaning aside from time.
We started on our way home as it was getting late. (= because)
We should hire the first applicant as he has more experience in the field. (= because)
This is the reason why students get confused during written exams. The three words – as, since, and for – can switch meanings from time expressions to reason expressions.
Meaning and Type of Words
Hope you learned something!