As ( time ) : when two things happen together
You can use AS when  two things happen at  the same time or over the same period of time.
I watched  her as she opened the letter.
As they walked along the street, they looked in the store window.
Turn off the light as you go out, please.

As ( time ) :
We use AS especially for two short actions happening at the same time.
George arrived as I left. (he arrived and I left at the same time)
We all waved goodbye to Tom as he drove away in his car.

As ( time ) :
You can also  use JUST AS ( exactly at the same time)
George arrived  just as I left.
Just as I sat down, the phone rang.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s