No one is ever allowed to call Prince George, Princess Charlotte and Prince Louis by this 'slang' word - and it's a rule that also applies to other royal children.
From the best parenting rules we've learnt from Prince Harry and Meghan Markle and Kate Middleton's parenting style to the parenting rule Prince William is 'scrupulous' about, the Royal Family has its own rules for raising children.
And there is one strict rule in place which prevents others from calling their children by an everyday word, a royal author has claimed.
Prince William and Kate Middleton are said to have issued strict instructions to their staff too.
Royal author Louise Heren spent a year at the Norland College in Bath where she researched a documentary, so she knows exactly what the nanny students are taught.
Speaking to The Mirror, she revealed there's one word the women are taught never to say: kids.
"Instead, the little royals should always be referred to as children or by their names. Louise said: "The word kid is banned. It's a mark of respect for the children as individuals."
But it can be a tricky one to avoid as the word kids is often a quicker and informal way of referring to a group of children without having to remember all of their names too.
Prince George, 10, Charlotte, eight, and Louis, five, have a nanny Maria Teresa Turrion Borrallo, who helps Kate and William juggle parenting with their royal duties, and it's likely that Maria learned the same rule when she was at the school.
It comes after Kate Middleton's 'no pushover' tactic was revealed, and Louise believes that Kate and Maria will be working closely together to raise the Wales children, "Given what we have seen of Catherine when she is out in public, she's very hands-on. I imagine her relationship with Maria is very close and they collaborate greatly on the care of the children."
She added, "I've spoken to nannies who have worked with other royal families and life is pretty normal. You get up, have breakfast, you go to school and you wear your school uniform whether you like it or not."
In other royal news, Prince Archie and Princess Lilibet might have just had a secret-family reunion with this special relative - and we’re sure Prince Harry was delighted and Prince George and Princess Charlotte will reportedly ‘attend boarding school together’ after ‘heated debates’ between Prince William, Kate Middleton and King Charles III over the children's future
