Mercury is the smallest planet in the known solar system and also closest to the sun.  This planet is named for the messenger of the gods in Roman mythology, who travelled at the speed of thought, appropriate here since Mercury's orbital period is the shortest of the known solar planets (88 days).  Mercury's astrological orientation is thought to influence one's intellectual aspects, and like the other six planets in traditional astology, it rules at least one astrological sign and falls in one sign.  This generally means that the planet's influence is exerted most strongly when found in the signs which it rules, but most feebly when in the sign of its fall.

The zodiacal colour of the planet Mercury is yellow, but orange is the colour of Mercury's associated kabbalistic sefirah (divine emanation), Hod (Splendour).  Mercury (L:  hydrargyrum; Heb:  kespith) is the alchemical metal associated with the planet Mercury.

The day of the week assigned to Mercury is Wednesday, whose Anglish name is derived from the Norse god Odin (Woden), god of wisdom.  In Romance languages, this day is assigned to Mercury: