When US rapper Kendrick Lamar tours Australia later this year, think twice before expertly dropping all the lyrics to HUMBLE.

Video has emerged of the Pulitzer Prize-winning artist interrupting a show in Alabama to ask a white fan to refrain from singing the N-word in his lyrics.

The fan had been invited onstage at the Hangout Festival at Gulf Shores, where Lamar was the headlining act, to rap his 2012 hit M.A.A.D city, which contains the racial slur a total of 15 times.

Sorry, this video has expired White fan invited onstage by Kendrick Lamar begs him to let her finish song despite shouting 'n*****'

Accounts posted online by concertgoers said the fan, named Delaney, was halfway through rapping the song when Lamar asked her to stop and cut the music.

"Aren't I cool enough for you?" she asked over boos from the crowd.

"You've got to bleep one single word, though," Lamar told her.

"Oh I'm sorry, did I do it? I'm so sorry. Oh my God," she replied.

Lamar then asked the crowd if she should be allowed to stay onstage and they responded with a mixture of boos and cheers.

"No, please keep me up here. I got you … I promise. I'm sorry about that," she said.

Eventually she was kicked off the stage for not knowing the song well enough.

Interruption has fans asking: 'When is it OK?'

Fans were divided on social media on whether it was appropriate for Lamar to scold a fan for rapping his own lyrics.

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But others argued it was never OK for white fans to sing the word.

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So what do the experts think?

Associate professor Darin Flynn teaches rap linguistics at the University of Calgary in Canada.

He says while some white hip-hop fans find it hard to understand why they can't say the N-word, he would advise them not to use the term.

"The truth is, free speech allows people to say and sing whatever they like, but it's honestly good advice for white hip-hoppers to avoid it. It'll just get you into trouble," he said.

"Even Eminem's disturbed alter-ego Slim Shady knows better than to say the N-word."

Writing for The Conversation, Professor Flynn elaborated that the N-word was a racial slur once understood to mean someone who was subservient, lazy, violent and simple-minded.

However, he said the black community had been able to reclaim the word, and it was now used in hip-hop music to oppose and change its meaning from something derogatory into something empowering. Though white people — including Eminem — are unable to use the word with the same effect.

"Because Eminem is white, he cannot subvert the N-word as non-derogatory, as black hip-hoppers can with each other," he explained.

"Only the in-group members that the slur was originally intended to target can [do that]."

And if you're still confused…

Here's another explanation from American author and journalist Ta-Nehisi Coates, who argues that not every word belongs to everyone.

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Alabama was the setting for some of the most important events of the American Civil Rights Movement in the 1950s, including the Montgomery Bus Boycott in 1955.

Lamar, whose song HUMBLE came in at number one in the triple j Hottest 100 this year, will headline the Splendour in the Grass music festival in Byron Bay in July this year.

He will also play shows in Perth, Melbourne, Adelaide and Sydney.