as while or when?

[keannu]

The following examples are explained in a grammar book like this.
2's "as" is more like a simultaneous action with "gained", while 1's "as" is a background action of "while". Do the two "as" give different nuances or the same?
If different, what is the standard to tell each other?

1. He sat watching her as she got ready.http://endic.naver.com/enkrEntry.nhn?entryId=594b0aede2a24df69a994ca368af23d3&query=AS#
2. As she grew older she gained in confidence.http://endic.naver.com/enkrEntry.nhn?entryId=594b0aede2a24df69a994ca368af23d3&query=AS#

 

[J&K Tutoring]

1. He sat watching her as she got ready.
2. As she grew older she gained in confidence.

In these two examples, as means the same thing.
1. The watching and the getting ready happen at the same time.
2. The gaining in confidence and the growing older happen at the same time.

 

[Raymott]

The following examples are explained in a grammar book like this.
2's "as" is more like a simultaneous action with "gained", while 1's "as" is a background action of "while". Do the two "as" give different nuances or the same?
If different, what is the standard to tell each other?

1. He sat watching her as she got ready.
2. As she grew older she gained in confidence.

The nuances are different, and you've just told us how. In 1. you can replace 'as' with 'while', but you can't in the second. You can't substitute 'when' for either. Both are ongoing actions.
The good news is that they mean close enough to the same thing that most people wouldn't give it a second thought - except that most natives wouldn't write, "While she grew older, she gained in confidence."

 

[keannu]

The nuances are different, and you've just told us how. In 1. you can replace 'as' with 'while', but you can't in the second. You can't substitute 'when' for either. Both are ongoing actions.
The good news is that they mean close enough to the same thing that most people wouldn't give it a second thought - except that most natives wouldn't write, "While she grew older, she gained in confidence."

As I searched in another website explaining the difference between as and while,
both are all ongoing actions, but the difference is that "as" is for an action that "develops or changes", while "while" is for just a background action, right?

If some action changes or develops, it deserves to go with "as", I guess.
For example,
while(x as x) I was playing baseball, my brother talked on the phone.

But in George Michael's "Careless Whisper", does the following two "as" mean "while" as in 1 or "progressing" as in 2?

"as I take your hand and lead you to the dance floor
as the music dies, something in your eyes
calls to mind the silver screen
and all its sad good-byes...."

 

[Raymott]

As I searched in another website explaining the difference between as and while,
both are all ongoing actions, but the difference is that "as" is for an action that "develops or changes", while "while" is for just a background action, right?
I wouldn't explain it that way. If there is action in the background, something is developing or changing. But that's how your grammar book describes it. If it makes sense to you, that's its purpose.

If some action changes or develops, it deserves to go with "as", I guess.
For example,
while(x as x) I was playing baseball, my brother talked on the phone.

But in George Michael's "Careless Whisper", does the following two "as" mean "while" as in 1 or "progressing" as in 2?

"as I take your hand and lead you to the dance floor
as the music dies, something in your eyes
calls to mind the silver screen
and all its sad good-byes...."
Here, 'as' does not mean 'while'

Here's how I see it:
With 'as', there is a connotation that the two events are linked; that an incremental change in one is associated with an incremental change in the other. That is the meaning of "2. As she grew older she gained in confidence." There is a necessary relationship between getting a bit older and becoming a bit more confident. In this case, we don't use 'while'.

'While', on the other hand, does not necessarily relate to linked events. "1. He sat watching her as she got ready." You can change 'as' to 'while' here. He watched her throughout the whole of the period of time that she got ready. Nothing changed in him as a result of the action of her. If the sentence had been, "As she got ready, he watched her ever more closely", then you can see that there is an incremental change that links both actions. She is a bit more ready, and he watches her a bit more closely. You can't change this to 'while' without losing this nuance.

In the song above, 'as' doesn't mean 'while', because there is the connection between the events such as I've described.