Say it too loudly within earshot of the wrong person and you could end up on a charge. But in a movie now being shown in Hong Kong, it is heard no fewer than 857 times.
It is 'the F-word', and it is still so controversial that on posters for the documentary of the same name, the 'u' has been replaced by an asterisk. But the director is unrepentant.
'It's one of the most famous words in the world,' Steve Anderson said in a telephone interview.
'A good film should cause a strong reaction, either good or bad.'
Examining the place in culture of 'the four-letter word', Anderson spoke to people who use it a lot, people who would never use it and those who do 'it' for a living.
He does not claim to be the vanguard of any battle against censorship, but he says audiences should be able to see what they want and make up their own minds.
'Filmmakers want to tell their story in every way, and [censorship] is certainly something they would fight against,' he said.