I don't understand why people still don't know that "Nigger" and "Nigga" are considered two completely different words.
And black people don't say "nigger".
I was rewatching "12 Years A Slave" last night and was thinking about this very same thing. Back then, southerners pronounced it "nigga" (which, for all intents and purposes, meant "nigger").
So maybe that's where the confusion comes from; depending on who's saying it, "nigga" may very well be "nigger"....just with an accent. If an uninformed person hears a racist white person says "nigga", then that person would probably associate ALL variations of the word as equally offensive.
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As for today's usage: well....I'm pretty sure that that horse has been beaten already in this thread. But as for me, I use it to refer generally to other black people (not just as "pal" or "friend" that I read when skimming the thread). Like when I'm talking to my brother: "Hey nigga, mom said call her." Or "you dumb nigga." I'm not using it as a substitute for "pal" or "friend"...I'm using it to reference the fact that he's black and I'm addressing him.
But sometimes I'll even refer to a WHITE person as "nigga" (which obviously doesn't make any sense), but....whatever. lol And I know other black people do it, too. I guess it just evolved to the point where black people use it as a way to refer to ANY person.
"Have you seen 'Powder'? That nigga was so pale"
But I typically avoid saying it in front non-black people though (because I don't want that to imply that I'm giving anyone the green light to say it in front of me).