What is the core of Harry Potter’s wand in the Harry Potter books?

Harry Potter’s wand has a phoenix-feather core in the Harry Potter books.

The wand is eleven inches long and made of holly. Its phoenix feather came from Fawkes, Albus Dumbledore’s phoenix. Garrick Ollivander explains that the feather produced another wand, belonging to Tom Riddle, creating a significant connection between Harry’s wand and Voldemort’s wand.

That connection becomes important when the two wands meet in combat. Their matching cores cause the rare Priori Incantatem effect during their duel in the graveyard in Harry Potter and the Goblet of Fire. The wand core is often confused with the wand’s wood: holly describes the material, while phoenix feather describes the magical substance inside it. Harry’s wand is therefore not made from phoenix feathers; only its core is.