Samir Hussein/WireImage Kate Middleton, now titled Catherine, the Princess of Wales.
The great debate begins again following the accession of her father-in-law King Charles III to the throne upon the death of his mother, Queen Elizabeth. Charles then passed his Prince of Wales title to his eldest son and heir William, making William's wife the Princess of Wales, as his mother Diana once was before.
Popularly known as "Kate" — and most widely searched online as Kate Middleton — the new Princess of Wales prefers to go by Catherine. As the crown shifts, PEOPLE plans to refer to the royal as Princess Catherine and the Princess of Wales. However, in headlines and upon first reference, Kate Middleton will remain so readers can quickly find the stories they are searching.
(Very technically, according to the experts at Debrett's, a U.K. authority on etiquette and titles, she is properly styled as Catherine, Princess of Wales rather than "Princess Catherine." Also technically correct: Princess William of Wales.)
Catherine retains her status as the Duchess of Cambridge, a title she's been known by since her 2011 wedding day. She has also acquired a new Duchess title, the Duchess of Cornwall, which formerly belonged to her mother-in-law, Camilla, the new Queen Consort.
"Queen Consort" refers to a Queen who is married to a King, rather than a Queen who has inherited the throne as Queen Elizabeth did. Elizabeth's husband, Prince Philip, was styled as Consort to the Queen. Popularly, Camilla will be known as Queen Camilla. When William eventually accedes to the throne, the same rules will apply to Catherine.
With the turn of a new page in royal history, we're breaking everything down:
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What's in a Name?
Catherine Elizabeth Middleton was born in Reading, England, and grew up in Bucklebury, Berkshire. Known and loved among family and friends as Catherine, she became nicknamed "Kate" by the time she went to St. Andrews University in Scotland, where she met her future husband.
Prince William and the palace regularly reference her as "Catherine" in statements and formal communications, though the public and press colloquially call her Kate, as do some of her own friends. By the books, she's been ennobled as Her Royal Highness the Duchess of Cambridge since she said "I do" to Prince William on April 29, 2011. The titles were bestowed upon them by Queen Elizabeth to mark their marriage and new life together.
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Shortly after Buckingham Palace announced that the Queen died on September 8, William and Kate's official social media accounts were updated as belonging to the "Duke and Duchess of Cornwall and Cambridge." The Duke of Cornwall is traditionally held by the eldest son of the reigning British monarch, with his wife taking the Duchess title.
In his first address as King the following day, Charles confirmed that his eldest son and daughter-in-law would now be known as the Prince and Princess of Wales. The top title is typically given to the eldest son of the monarch who is heir apparent. The Queen's uncle Edward VIII held the title for the bulk of his life before acceding to — and, within months, abdicating — the throne.
Confirming the retention of their duchy rank, the Buckingham Palace website states that William and Kate "are now known as The Prince and Princess of Wales, having formally been known as The Duke and Duchess of Cornwall and Cambridge."
Unlike the title of Princess, Duchess is never used before a first name (i.e., "Duchess Catherine"). Instead, the correct usage is Catherine, Duchess of Cornwall and Cambridge. However, the Princess title is of higher rank and therefore will be primarily used. (Camilla never used the title of Princess of Wales in deference to the late Princess Diana.)
This styling is here to stay, until William succeeds his father on the throne one day. Then, Catherine will be formally known as the Queen Consort or popularly Queen Catherine, as Charles' wife Queen Camilla is now.
DANIEL LEAL/AFP via Getty Images From left: Princess Anne, Camilla, Duchess of Cornwall, Prince Charles, Queen Elizabeth, Kate Middleton, Princess Charlotte and Prince George and Prince William on the balcony for Trooping the Colour on June 2.
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What about their children?
As their parents ascend as Prince and Princess of Wales, the children are now Prince George of Wales, Princess Charlotte of Wales and Prince Louis of Wales.
The young royals were previously known as George Cambridge, Charlotte Cambridge and Louis Cambridge at school. Now they will be known to their friends and teachers as George Wales, Charlotte Wales and Louis Wales at Lambrook School, where they enrolled together earlier this month.
The new last name follows precedent set by their father. Because of his own father's position, William was known as William Wales during his school years at Eton and St. Andrews, and as Captain Wales in the army.