Because the difficulty of translating "Deathly Hallows" to other languages, JK Rowling created an alternate title for the translations: "Harry Potter and the Relics of Death". See more...
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Harry Potter and the Deathly Hallows - 7 mistakes
Continuity: Near the end of chapter thirty, it says that the only people left in the room of requirement are Harry, Ginny, Mrs Weasley, Lupin, Fred, George, Bill and Fleur. But on the next page Percy (who had recently entered the room) says sorry to Mr Weasley, but Mr Weasley had left the room along with all the other people.
Plot hole: In the chapter, "Prince's tale", there's a memory in which Snape and Lily are talking about the friends of each other (the memory begins with Snape saying "I thought we were friends"). In this memory, Lily says that James has saved Snape's life, but Snape says that he was only saving himself. Some lines before, Snape makes it clear that he doesn't know that Lupin is a werewolf. However, in "Prisoner of Azkaban", Lupin said (and Snape himself) that after James saved Snape's life, he knew that Lupin was a werewolf. So this memory doesn't match - if James already saved Snape's life, he should've known that Lupin was a werewolf. (And that's why he would say that James was only saving himself).
Factual error: Harry et al. are captured by Death Eaters in March (it's mentioned part way through chapter 22 that Ron was unable to find Potterwatch on the radio until one night in March; they are captured shortly after the program ends). Greyback and the other Snatchers take Harry and his friends to Malfoy Manor, and Narcissa states that, if this is indeed Harry Potter, her son, Draco, will recognize him. She says he is home on Easter break. However, this is 1998 (Harry turned 17 near the beginning of the book, which would've made it 1997, and this was the following March), and Easter was April 12th that year. Draco would still be at school.
Continuity: When Harry, Ron, and Hermione leave the Great Hall after the Battle of Hogwarts ends, Harry is under his invisibility cloak, and remains under it when they reach the Headmaster's office. When Harry raises his arms to silence the headmaster and headmistress portraits, he is suddenly visible to everyone, but there's never any mention of him taking the cloak off.