DEG

1 During or while?

Compare these examples.

2 By or until?

Compare these examples.

We can use by the time or until before a clause, e.g. we arrived.

3 As, like and as if/as though

Compare these examples.

We can also use as or like before a clause.
We drive on the left here, as/like you do in Britain.
Mike and Sarah are going to Paris for the weekend, as/like they did last year.
Like is more informal than as before a clause.

We also use as with verbs of speaking and knowing, e.g. say, know, expect.
As I said before, I'm sorry. (= I'm sorry, and I said so before.)
I haven't much money, as you know. (= I haven't much money, and you know it.)
Rachel arrived late, as we expected. (= We expected her to arrive late, and she did.)

We use as if/as though before a clause to say how something seems.
Tom looks really awful. He looks as if/as though he's been up all night.
Nick can be a difficult person. He sometimes behaves as if/as though he's the only one with problems.