How many Muses inspire arts and sciences?

The story behind the answer

The Muses are nine in number—the daughters of Zeus and Mnemosyne (Memory)—who inspire the arts and sciences. Classical sources name them: Calliope (epic), Clio (history), Euterpe (music), Thalia (comedy), Melpomene (tragedy), Terpsichore (dance), Erato (love poetry), Polyhymnia (hymns), and Urania (astronomy). They often accompany Apollo on Mount Helicon or Parnassus.

Memory tip: think 3 × 3—classical perfection—since Zeus spent nine nights with Mnemosyne to beget them. Or picture Apollo conducting a “nine-track” playlist covering every major art and science. That’s why the correct answer is 9.