What name does Tolkien give to the cataclysm that destroys Númenor?

Tolkien calls the cataclysm that destroys Númenor the Akallabêth.

Akallabêth is a Quenya title meaning “The Downfallen.” It is the name of one of the principal sections of The Silmarillion and recounts the downfall of Númenor, the island kingdom founded for Men who had aided the Elves during the First Age.

In the story, Númenóreans become increasingly fearful of death and jealous of the Elves. Their king, Ar-Pharazôn, challenges the Valar and sails westward with a great fleet. As a consequence, Númenor is overwhelmed and the shape of the world is changed; the surviving Faithful escape under Elendil.

Akallabêth is also a title in Tolkien’s invented languages, so it can be confused with the event’s English description, “the Downfall of Númenor.” The two expressions refer to the same central catastrophe.