1. Another double standard is society.
Black-Black is okay as long as they are friends because then it can substitute for homie
etc. If mad, then it once again becomes unacceptable. However, no other race, ESPECIALLY caucasians, can use it without fear of it being taken offensively. Occasionally though, if the black likes another non-black person enough, then it can become acceptable. (Although they could both get in trouble if other blacks hear it)
2. Derived from the derogative term "nigger
", usually connected as a condescending name from a white to a black person.
3. Also considered different from it's root word "nigger". This has been best defined from rap celebrity/legend Tupak Amaru Shakur who stated "Nigger - a black man with a slavery chain around his neck; Nigga - a black man with a gold chain on his neck."