As = at the same time as
You can use as when two things happen at the same time:
– We all waved goodbye to Liz as the drove away.
(we waved and she drove away at the same time)
– I watched her as she opened the letter.
– As I walked along the street, I looked in the store windows.
– Can you turn off the light as you go out, please?
Or you can say that something happened as you were doing something else (in the middle of doing something else):
– Jill slipped as she was getting off the bus.
– We met Paul as we were leaving the hotel.
For the past continuous (was getting / were going, etc.), see Unit 6.
– Just as I sat down, the phone rang.
– I had to leave just as the conversation was getting interesting.
We also use as when two things happen together in a longer period of time:
– As the day went on, the weather got worse.
– I began to enjoy the job more as I got used to it.
the day went on
the weather got worse
As the day went on, the weather got worse.
Compare as and when:
We use as only if two things happen at the same time.
– As we walked home, we talked about what we would have for dinner.
(= at the same time)
Use when (not as) if one thing happen after another.
– When we got home, we started cooking dinner.
(not As we got home)
As = because
As sometimes means “because”:
– As it was a national holiday last Thursday, all the banks were closed.
(= because it was a national holiday)
– The thief was difficult to identify as he was wearing a mask during the robbery.
We also use since in this way:
– Since it was a national holiday last Thursday, all the banks were close.
– The thief was difficult to identify since he was wearing a mask during the robbery.
Compare as with when:
– I couldn’t contact David as he was on a business trip, and he doesn’t have a cell phone. (= because he was on a trip)
– As they lived near us, we used to see them pretty often.
(= because they lived near us)
– David’s passport was stolen when he was on a business trip.
(= during the time he was away)
– When they lived near us, we used to see them pretty often.
(= at the time they lived near us)