Since

We use since as a preposition, a conjunction and an adverb to refer to a time, and as a conjunction to introduce a reason.

Since: time

We use since to refer back to a previous point in time. We use since as a preposition with a date, a time or a noun phrase:

It was the band’s first live performance since May 1990. (since + date)
I have been happily married for 26 years, since the age of 21. (since + noun phrase)

We also use since as a conjunction to introduce a subordinate clause:

It’s so long since I saw them. (since + clause)
Lenny had slept most of the way since leaving Texas. (since + clause)
He’s been back to the office a few times since he retired. (since + clause)

Since and tenses

When since introduces an action or event at a point of time in the past, we can use the past simple or present perfect after since and the present perfect in the main clause:

They haven’t received any junk mail since they moved house.
They haven’t received any junk mail since they’ve moved house.

We can use the past simple, present perfect or past perfect after since with the expression it + be + time + since:

It’s been years since I rode a bike. (it’s = it has)
It’s been years since I’ve ridden a bike. (it’s = it has)
It’s years since I rode a bike. (it’s = it is)
It’s years since I’ve ridden a bike. (it’s = it is)
It’d been years since I’d ridden a bike. (it’d = it had)

It’s been years since … is more common in American English than It’s years since ….

When since introduces a state in the past that is still continuing in the present, we use a present perfect form of the verb after since and a present perfect form of the verb in the main clause:

Since I’ve been back at work, I’ve been feeling great.

Since + -ing

We can use since + -ing form to refer to time when the subject of the verb is the same in the main clause and the subordinate clause:

Since leaving school, he has had three or four temporary jobs. (Since he left school, he has …)
Since moving from a Chicago suburb to southern California a few months ago, I’ve learned how to play a new game called Lanesmanship. (Since I moved …, I’ve learned …)

Since, since then

We can use since or since then as an adverb of time when the time reference is understood from the context:

His father doesn’t talk to him. They had an argument a couple of years ago and they haven’t spoken since. (since they had the argument)
They bought the house in 2006 and they’ve done a lot of work on it since then. (since 2006)

We use ever since as a stronger form of since or since then:

When I was young, I had a little collie dog, but one day he bit me really badly. I’ve hated dogs ever since.

Since: reason

We use since as a subordinating conjunction to introduce a subordinate clause. We use it to give a reason for something:

Sean had no reason to take a taxi since his flat was near enough to walk to.
Since her husband hated holidays so much, she decided to go on her own.
They couldn’t deliver the parcel since no one was there to answer the door.

Since: typical errors

We don’t use since with extended periods of time. We use for:

She was waiting for four hours.
Not: ~~She was waiting since four hours.~~

We use since, not from, with a clause referring back to a point in time:

I’ve been swimming since I was three years old.
I’ve been swimming from the age of three.
Not: ~~I’ve been swimming from I was three years old.~~

We use since, not once, to introduce a reason:

I think I should have my money back since I didn’t have what was promised in the brochure.
Not: ~~I think I should have my money back once I didn’t have~~ …

We use since, not ago, after ‘it’s a long time’ when we refer back to a point in time:

It’s a long time since your last letter.
Not: ~~It’s a long time ago your last letter.~~

Since: time​

Since and tenses​

Since + -ing​

Since, since then​

Since: reason​

Since: typical errors​