The conjunction as has several different meanings. We use as when one event happens while another is in progress (‘during the time that’). In this case the verb after is often in the continuous form:
They arrived as we were leaving. (time conjunction meaning ‘while’ or ‘when’)
We use as to connect a result with a cause:
I went to bed at 9 pm as I had a plane to catch at 6 am. (reason and result meaning ‘because’)
We also use as to mean ‘in the way that’:
As the forecast predicted, the weather was dreadful for the whole of the weekend.
She arrived early, as I expected.
The same as
We use as with the same to talk about identical things:
We use as to introduce two events happening at the same time. After as with this meaning, we usually use a simple (rather than continuous) form of the verb:
As the show increases in popularity, more and more tickets are sold daily.
Compare
When you get older, moving house gets harder.
One thing happens first and as a result the second thing is true.
As you get older, moving house gets harder.
Not: While you get older …
The two things happen at the same time.
Warning:
We don’t use as alone to introduce examples. We say such as:
They gave them gifts such as flowers and fruit and sang a special welcome song.
