Titania (moon) numerals, and since then Titania has been designated '. Shakespeare's character's name is pronounced , but the moon is often pronounced , by analogy with the familiar chemical element titanium. The adjectival form, "Titanian", is homonymous with that of Saturn's moon Titan. The name "Titania" is ancient Greek in origin, meaning "Daughter of the Titans". Titania orbits Uranus at the distance of about , being the second farthest from the planet among its five major moons. Titania's orbit has a small eccentricity and is inclined very little relative to the equator of Uranus. Its orbital period is around 8.7 days,
Double planet the four, small, outer satellites of Pluto. A now-abandoned hypothesis for the origin of the Moon was actually called the "double-planet hypothesis"; the idea was that the Earth and the Moon formed in the same region of the solar system's proto-planetary disk, forming a system under gravitational interaction. This idea, too, is a problematic condition for defining two bodies as "double planets" because planets can "capture" moons through gravitational interaction. For example, the moons of Mars (Phobos and Deimos) are thought to be asteroids captured long ago by Mars. Such a weak definition would also deem Neptune-Triton a double planet,