Please teach me how to use "AS"

[mooyong]

I have seen many word and many people say "AS", I would like to know how to use it.

I read in the intranet I understand when the sentense use 2 AS for Example : I'm not well english as same as you ---> it mean you and me not well english is similar

But when the sentence use 1 as I don't clear what is it mean, for example The music lylics

Close your eyes
And I will be swimming
Lullabies fill your room
And I will be singing
Sing to only you
Don't forget I'll hold your head
Watch the night sky fading red​

But as you sleep
And no one is listening
I will lift you off your feet
I'll keep you from sinking​

I don't sure AS is mean " you like sleep " or not​

And please teach me how to use " AS"​

 

[Tdol]

As you sleep = when you sleep

 

[mooyong]

As you sleep = when you sleep

Thank you so much Tdol.

Do you know how to use "AS" in the sentense if you Know please teach me how to use it.

Thank so much

 

[sarat_106]

Thank you so much Tdol.

Do you know how to use "AS" in the sentense if you Know please teach me how to use it.

Thank so much

‘As’ is a word which does many functions. It can be used as conjunction, preposition, relative pronoun, and adverb

1. Examples of use as conjunction (having different meanings):
§ I decided to book into a hotel, as it was getting late. (meaning; because)
§ I saw him as I was coming into the building. (meaning; while)
§ He got divorced, as his parents had done years before. (in the same way)
§ Angry as he was, he couldn't help smiling. (though)

2. As preposition
§ He is acting as a mediator to settle the dispute.
§ John has been appointed as captain of the team.

3. As adverb
§ The child sang as sweetly as a nightingale.
§ I don't think it's as hot and humid today as it was yesterday.
§ He left as agreed.

4. As relative pronoun
§ I have the same trouble as you had.
§ She did her job well, as can be proved by the records.

These are only a few tips. Please go to a good dictionary on the web to learn in great deiail.