You got it: because, cuz, cos, 'cause, all have the same meaning BUT cuz and coz are the sloppy way of writing "because". This is poor English. Really good to know this, and even better to never use it.

They are not official words of the English language. They are slang words (more known as text speak) You can find the use of these words in mobile chat or online in internet chatrooms. "Cuz" and "cos" both mean "because"

Neither cuz nor cos are proper words.

Normally in literature, when the author wants to express this pronunciation of "because", they spell it like this.... 'cause. With an apostrophe (') before the "c". Example: I write this way 'cause that's how I speak. It is pronounced the same as "coz" or "cos", which as Darkling said, are used in "text speak" because they are shorter.

"cuz" is slang for because, I have never hear someone use "cos" though Also to give you more information about "nada" in your other question, "nada" is Spanish for nothing, but some people say it as slang