Mastering time-related prepositions and adverbs like Since, for, from, ago is essential for accurate English grammar, particularly when discussing tenses, durations, and specific points in time.
What is the Difference Between Since, For, From, and Ago?
Understanding how to use since, for, from, and ago correctly ensures your English sentences follow proper tense rules and structural logic. Below is a comprehensive guide based on traditional grammar rules.
Core Definitions and Time References
Each time marker serves a specific grammatical function regarding duration or points in time:
- For refers to a space of time or duration.
- Since and from refer to a point of time.
- While since refers only to a past point, from refers to a point of time across all tenses (explore related time prepositions).
Examples of Basic Time Markers
- He has been here for a week.
- I have not seen you for many days.
- It is many days since I saw you last (since the point of time that I saw you last).
- He has been here since Monday last.
- He began English from the age of ten (past).
- He begins English from today (present).
- He will begin English from tomorrow (future).
How to Use Since and Ago as Adverbs
As adverbs, since and ago often mean the same thing. Thus, you can write either "I saw him long ago" or "long since." Note that long since equals long ago (and should not be phrased as "for a long time").
If ago is used and the event to be dated is introduced by a clause, it should not be followed by the conjunction since but should instead use the conjunction that.
- It was ten years ago that (not since) he died.
- Alternative constructions: It is ten years since he died. OR He died ten years ago.
Using "ago since" together is tautological because adverbially "since" equals "ago."
Incorrect vs. Correct Usage of Ago and Since
| Incorrect Sentence | Correct Alternative |
|---|---|
| It is five years ago since he came here. (Incorrect). | He last came here five years ago. (Correct). |
| - | It is five years since he came here. (Correct). |
What Are the Different Uses of 'Since'?
The word since functions in multiple ways across different parts of speech in English grammar.
1. Since as an Adverb
As an adverb, since has two distinct meanings:
- From some past time up to now:
- I met him three years ago and have known him ever since.
- He said that he had been healthy since.
- The price was high last year; but it has come down since.
- I was with him at school; but have seen him only thrice since.
- Ago:
- I saw him two months since.
- He died long since.
2. Since as a Preposition
As a preposition, since means "from," and is placed before a noun or a phrase denoting some past point of time, and is preceded by a verb in the Perfect Tense:
- I have been since yesterday.
- He has been here since January last.
- They have been here since the 5th instant.
3. Since as a Conjunction
As a conjunction, since means "from the time when," and is followed by a clause with a verb in the Past Indefinite and preceded by a verb in the Present Indefinite or Present Perfect:
- I have been ill since you saw me last.
- It is a month since I saw you last.
- They have been absent since you left the place.
Key Takeaways
- For measures a duration of time, whereas since and from pinpoint specific starting points.
- Never combine ago and since in the same sentence as a tautology.
- Since can function grammatically as an adverb, a preposition, or a conjunction depending on the sentence structure.
Quick Practice
Test your understanding of these rules by writing your answers in the comments below:
- Write a correct sentence using since as a conjunction with a Present Perfect verb in the main clause.
- Correct this phrase if needed: It is three years ago since they met.
Frequently Asked Questions
What is the difference between for and since?
For is used to describe a duration or space of time (e.g., for three years), while since marks a specific starting point in the past up to the present (e.g., since 2020).
Can we use ago and since together?
No, using ago and since together (such as "it is years ago since...") is incorrect and tautological. Choose one or the other.
How does 'since' function as a conjunction?
As a conjunction, it means "from the time when," connecting a main clause in the present tense with a dependent clause in the past indefinite tense.