Which Harry Potter book is the only one titled with the word “Deathly”?

Harry Potter and the Deathly Hallows is the only Harry Potter book titled with the word “Deathly.”

The novel is the seventh and final book in the main Harry Potter series. Bloomsbury published it in the United Kingdom on 21 July 2007, while Scholastic released it in the United States on the same date.

Its title refers to three legendary magical objects: the Elder Wand, the Resurrection Stone, and the Invisibility Cloak. Together, these objects form the Deathly Hallows of the story's mythology.

The book follows Harry, Ron, and Hermione as they leave Hogwarts to search for Horcruxes and oppose Lord Voldemort. It is distinct from Harry Potter and the Half-Blood Prince, the sixth novel, whose title refers to a different character and mystery.