Arresto Momentum

• Incantation: Arresto Momentum
• Pronunciation: uh-REST-oh mo-MEN-tum
• Wand Movement: Unknown
• Light: Unknown
• Effect: A spell that decreases the velocity of a moving target, either slowing it down significantly or bringing it to a complete halt.
• Type: Charm

While the incantation “Arresto Momentum” is not explicitly used in the original seven novels, a spell with an identical effect is notably performed by Albus Dumbledore. During a Quidditch match against Hufflepuff in 1993, Harry Potter is attacked by a group of Dementors and falls from his Nimbus Two Thousand. Before Harry can hit the ground, Dumbledore casts a non-verbal spell that visibly slows his descent, saving his life. The verbal incantation is widely used in other media within the wizarding world:

• In the film adaptation of Harry Potter and the Prisoner of Azkaban, Albus Dumbledore verbally shouts the incantation to save Harry from his fall (film).
• Hermione Granger uses the spell to cushion her, Harry Potter, Ron Weasley, and Griphook's landing after being thrown from a cart into the Lestrange Vault at Gringotts Wizarding Bank (film: Harry Potter and the Deathly Hallows – Part 1).
• Newt Scamander casts it to save a baby Niffler that had fallen from a jewelry store display (film: Fantastic Beasts and Where to Find Them).

The difficulty of learning this Charm is not specified in the novels. As Dumbledore was able to perform a version of it non-verbally with great precision and power, it can be assumed that advanced wizards can master it to a high degree. There are no known specific counter-spells. The effect can likely be overcome by casting a spell that re-applies force or motion to the targeted person or object.

The incantation is derived from a combination of Latin and pseudo-Latin words.

• Arresto is a pseudo-Latin word derived from the English “arrest,” which comes from the Old French arester, meaning “to stop” or “to stay.”
• Momentum is a direct borrowing of the Latin word for “movement, motion, moving power.”

The combination literally translates to “stop movement,” which accurately describes the spell's function.

The incantation Arresto Momentum was created for the film adaptation of Harry Potter and the Prisoner of Azkaban. In the novel, Dumbledore saves Harry with a swift, non-verbal spell. The film added the verbal incantation to make his actions clearer to the audience. Due to its prominent use in the films, the spell has become widely recognized by fans and has been incorporated into other official media, including the Fantastic Beasts film series and video games such as Hogwarts Legacy, where it is a learnable Charm used in combat and for solving puzzles (video game).