<P> Professor Trelawney first appears in the third book of the series, when Harry, Ron, and Hermione start divination lessons . The friends generally believe Professor Trelawney is a fraud . However, Gryffindor students Parvati Patil and Lavender Brown are very fond of and impressed by her . According to Professor McGonagall, her credibility as a Seer is undermined by her habit of erroneously predicting, each year, the death of one of her students . Her more profound predictions seem only to happen when she is in a trance and unaware of what she is saying, with no memory of it afterward . However, almost all her predictions were later shown to be true in the books even if she was not in a trance . </P> <P> Prior to the events of the Harry Potter books, Professor Trelawney falls into a prophetic trance while in an interview with Dumbledore at the Hog's Head, making a prophecy about the birth of a wizard "with the power to vanquish" Voldemort . This prophecy was partly overheard by Snape, who relayed what he heard to Voldemort . This led Voldemort to attack the Potter family, believing that Harry was the child named . In Harry Potter and the Prisoner of Azkaban, Professor Trelawney prophesies to Harry about the events of the book's climax . In Order of the Phoenix, Professor Trelawney is first put on probation by Umbridge, and later fired . However, Professor Trelawney continues to reside in Hogwarts castle due to an order by Dumbledore, who believes that she would be in danger outside Hogwarts due to the prophecy she made during her interview . Dumbledore later reveals that the prophecy is why he keeps her employed as a Divination teacher . Professor Trelawney returns to teaching in Half - Blood Prince, but has to share classes with Firenze, as he was cast out by his fellow centaurs when he agreed to replace Professor Trelawney after she was fired, which she thinks is an outrage . In Harry Potter and the Deathly Hallows, she is seen aiding in the Battle of Hogwarts by magically accelerating her crystal balls at Death Eaters . She uses one of these crystal balls to defend an injured Lavender against the attack of werewolf Fenrir Greyback . In the film adaptation, Harry Potter and the Deathly Hallows--Part 2, she is seen covering someone's body, with the aid of Padma Patil . </P> <P> In the British editions of the books, her name is consistently spelled as "Sybill". In the American editions, from her first appearance in Prisoner of Azkaban through Order of the Phoenix, her name is spelled as "Sibyll". However, in the American edition of Half - Blood Prince, it is re-spelled as "Sybill", matching the UK edition . </P> <P> Professor Trelawney is portrayed by Emma Thompson in the Prisoner of Azkaban, Order of the Phoenix, and Deathly Hallows Part 2 . </P>

Who is the female professor in harry potter