Difference among since, for, as, because

[Sonia*]

Good Evening to all of you,

Kindly tell me the difference among "since","for","as","because". As I have noticed that these all the words have got the same meaning but we should be very carefull while using them.

Thanks a lot teacher.
Sonia*

[Morteza]

Hi!
Read the following examples,please!
I couldn't go to work because I was ill.
As/Since I was ill,I couldn't go to work.
I couldn't go to work for my illness.
"FOR =because" just in an old-fashioned way or in litterature,NOT in a common/ordinary language:
He can't stop loving her,for he really loves her.
Regards,
Morteza