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 she drove away. (We waved and she drove away at the same time) I watched her as she opened the letter.
Or you can say that something happened as you were doing something else (in the middle of doing something else):
Kate slipped as she was getting off the bus. We met Paul as we were leaving the hotel.
You can also use just as (= exactly at that moment):
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 1 got used to it.
As = because. As also means ‘because’:
As I was hungry, I decided to find somewhere to eat. (= because I was hungry) As it was a public holiday last Thursday, most of the shops were shut. (= because it was a public holiday)
You can also use since in this way:
Since we have plenty of time, let’s go and have a coffee. LIKE & AS
Like = ‘similar to’, ‘the same as’. You cannot use as in this way:
What a beautiful house! It’s like a palace, (not as a palace) What does Sandra do?’ ‘She’s a teacher, like me.’ (not as me) Be careful! The floor has been polished. It’s like walking on ice. (not as walking) It’s raining again. I hate weather like this. (not as this) In these sentences, like is a preposition. So it is followed by a noun (like a palace), a pronoun(like me / like this) or -ing (like walking).
You can also say ‘... like (somebody/something) doing something’:
‘What’s that noise?’ ‘It sounds like a baby crying.’
Sometimes like = for example:
Some sports, like motor-racing, can be dangerous.
You can also use suchas (= for example):
Some sports, such as motor-racing, can be dangerous.
As = in the same way as, or in the same condition as. We use as before subject + verb:
I didn’t move anything. I left everything as it was. You should have done it as I showed you.
Like is also possible in informal spoken English:
I left everything like it was.
We can say as usual / as always:
You’re late as usual. As always, Nick was the first to complain.
As can be used as a preposition, but it this case it has a different meaning. It means in the position of, in the form of etc. :
A few years ago I worked as a taxi driver. (not like a taxi driver) We haven’t got a car, so we use the garage as a workshop. Many words, for example ‘work’ and ‘rain’, can be used as verbs or nouns. London is fine as a place to visit, but I wouldn’t like to live there.
AS IF/AS THOUGH/LIKE
You can use as if or as though to say how somebody or something looks/sounds/feels:
That house looks as if it’s going to fall down. Helen sounded as though she had a cold, didn’t she? I’ve just come from holiday, but I feel very tired. I don’t feel as if I‘ve just had a holiday.
In informal spoken English you can also use like:
That house looks like it’s going to fall down.
You can say It looks as if ... / It sounds as if ... :
We took an umbrella because it looked as if it was going to rain. Do you hear that music next door? It sounds as if they are having a party.
You can also use as though or like:
It looks as though she isn’t coming, or It looks like she isn’t coming.
I don’t like Tim. He talks as if he knew everything. The meaning is not past in this sentence. We use the past (as if he knew) because the idea is not real: Tim does not know everything. She’s always asking me to do things for her - as if I didn’t have enough to do already.
When you use the past in this way, you can use were instead of was:
Why do you talk about him as if he were (or was) an old man? FOR, DURING & WHILE
We use for + a period of time to say how long something goes on:
for two hours for a week for ages We watched television for two hours last night. Diane is going away for a week in September. Where have you been? I’ve been waiting for ages. Are you going away for the weekend?
We use during + noun to say when something happens (not how long):
during the film during our holiday during the night I fell asleep during the film. We met some really nice people during our holiday. The ground is wet. It must have rained during the night.
With ‘time words’ (for example: the morning / the afternoon / the summer), you can usually say in or during:
It must have rained in the night, (or during the night) I’ll phone you sometime during the afternoon, (or in the afternoon)
We use during + noun, but while + subject + verb:
I fell asleep during the film. but I fell asleep while I was watching TV. We met a lot of interesting people during our holiday. but We met a lot of interesting people while we were having a holiday. BY & UNTIL BY THE TIME
By (+ a time) means not later than:
I sent the letter to them today, so they should receive it by Monday.(= on or before Monday, not later than Monday) We’d better hurry. We have to be home by 5 o’clock. (= at or before 5 o’clock, not later than 5 o’clock)
We use until (or till) to say how long a situation continues:
‘Shall we go now?’ ‘No, let’s wait until (or till) it stops raining.
It’s too late to go to the bank now. By the time we get there, it will be closed. = the bank will close between now and the time we get there) (from a postcard) Our holiday ends tomorrow. So by the time you receive this postcard, I’ll be back home.(= I will arrive home between tomorrow and the time you receive this postcard)
We can alsosay by then or by that time:
Karen finally arrived at the party at midnight, but by then (or by that time), most of the guests had left.