Above the pulsating beat of San Francisco's "Hip-Hop Nation" arts festival, 14-year-old Vienna Howard makes herself heard.

"I know why everybody gets upset about (the N-word)," said the African American eighth-grader from Oakland as she toured the Yerba Buena Center for the Arts exhibit a few days ago with her hip-hop class. "Back then, it was a bad word. But to me, slavery's over. Everybody says it now. It's no big thing."

Standing next to her, teacher Traci Bartlow, also black, said she considers the N-word to be profanity.

"It makes me uncomfortable," said Bartlow of Oakland's Eastside Arts Alliance. "I don't allow it in my classes."

Vienna and her teacher reflect the profound complexities of racism evoked by the word "nigger" -- the atom bomb of racial epithets in the American language, according to Harvard University law Professor Randall Kennedy.

Actress and singer Jennifer Lopez got a recent taste of that volatility when a furor erupted over her use of the word in a new remix of the song, "I'm Real" in her "J.Lo" album.

On the one hand, the N-word is a powerful reminder of the odious history of oppression of African Americans in this country.

"It's been part of the soundtrack of lynchings and other terrible things," Kennedy said.

On the other, the term has morphed into a ubiquitous moniker for youths of all colors, as rap artists and popular comedians like Chris Rock have popularized it beyond black communities as a term of affection.

"There are white kids in the Oakland Hills going around saying, 'What's up, my nigga?' " said youth worker Paul Billingsley, 19, of San Francisco.

That mainstreaming has been problematic for some blacks. For although African Americans hold a wide diversity of opinion about who "owns" the N-word and whether it should be used at all, many blacks would not be comfortable hearing it said by nonblacks.

"If someone outside the community uses it, there is and always will be a sense of mistrust, a sense that you have no right to use it because you could very well be using it in the old way," said San Francisco family psychologist Brenda Wade, who is black.

Whites have a particular burden to avoid the term, said Todd Boyd, University of Southern California professor of critical studies at the School of Cinema and Television, who has studied the term.

"You might hear someone say, 'Well, if a white person can't use it, that's unfair,' " Boyd said. "But for a white person to use this word evokes images from the past that are unacceptable. So you can't say it. The real point of the matter is that white people are offended because here is a rare instance where this is off-limits to you based on your race. It's something African Americans are accustomed to in this society."

After the song's release, New York City disc jockeys Star and Bucwild of WQHT-FM Hot 97 railed against Lopez for using a "derogatory" term against blacks and reportedly forwarded 3,000 protesting faxes and e-mails from listeners to Epic Records, Lopez's label. "What's next -- is Britney Spears going to come up on stage and say, 'What's up, my niggas?' " asked Star Torain, the DJ.

The South Bronx-raised Lopez, who not long ago broke up with rap megastar Sean "Puffy" Combs, told NBC's "Today" show that the accusation was "really absurd and hurtful to me."

"People say it's just a word -- why trip?" said Davey D, a disc jockey at the Bay Area's KMEL and KPFA radio and an authority on hip-hop. "But words go a very long way."

Davey D, who has long protested the excessive use of the N-word in rap lyrics, asserted that often rappers' use of the N-word doesn't reflect "endearment."

"Two years ago, Puffy (Combs) did a concert that had all ages and a very mixed crowd at the San Jose Arena," said Davey D. "There he was before a mixed audience, saying, 'F-- you bitch, f-- you nigga.' It was not being used as an endearment. The fact is, Puffy can be nigga all he wants but there are a bunch of black people who don't agree."

There have long been black critics of the proliferation of the N-word, he said, citing a college and community radio boycott 10 years ago against the rap group NWA (Niggaz With Attitude), a petition signed by 400 rap artists pledging not to use the N-word and, more recently, a call for a moratorium against the use of the word by all entertainers.

"But you don't see it on 'Nightline,' " said Davey D. "The implication is that there aren't any black people who don't like the term."

Project Islamic Hope wants to change that. After the Lopez flap, the Los Angeles-based advocacy group called for the moratorium on the use of the N- word by all artists.

The organization also protested the 1999 NAACP Image Awards given to rappers Jay-Z and Big Pun for recognizing "gangster rappers that call each other niggers and denigrate black women," said director Najee Ali.

And rappers are dealing with it on their own, said Ricky Vincent, a professor of black studies at San Francisco State University.

"A lot of performers have common sense about whether that word belongs in their work or not," Vincent said.

Lopez isn't the first and won't be the last to run afoul of the N-word.

Last month, Sen. Robert Byrd, D-W.Va., said the words "white nigger" in a Fox News interview and later apologized. In February, California Lt. Gov. Cruz Bustamante uttered the N-word while speaking to black trade unionists. He spent the next few months doing damage control.

"Nonblacks should view the word as blacks view it -- it's a dangerous word, " said Kennedy, who has written a book about the sociology of the term. "One should handle it with care."

Even black youths have gotten in trouble over the word. Last October, Nathan Martin, a senior at Buchanan High School in the Fresno County town of Clovis, was suspended two days after a white student overheard him greeting a fellow black student with "Whazzup" and the N-word.

African Americans who grew up in the civil rights era acknowledge the yawning generation gap between them and youths like Nathan, who have put a new face on the term.

To Kennedy, there is affirmation in the change. "The great thing is that this terrible word has been made into a boomerang -- just like gay people have made the word 'queer' a boomerang," he said. "You throw it back at your oppressors."

Tupac Shakur did so, giving "nigga" a new meaning: "Never Ignorant, Getting Goals Accomplished."

Long before hip-hop, the N-word had a multiplicity of meanings for blacks. In colloquial usage, the term can be neutral, purely descriptive or even a word of endearment, Kennedy said.

The meaning varies, depending on who's using it and the context -- generally, "nigger" has negative connotations, while "nigga" or "niggah" can connote friendship or comradeship.

The origins of the N-word are Latin, from "niger," meaning "black." Merriam- Webster's Tenth Edition Collegiate Dictionary defines the word as "a black person," although prefacing that with the caution that the term "ranks as perhaps the most offensive and inflammatory racial slur in English."

African Americans' growing consciousness of the N-word's many incarnations reflects an effort to come to grips with their complex relationship with the term.

"It's a black thing -- something the black community needs to resolve," Ricky Vincent said.