Mercury cultural definition

The Roman name of Hermes, the messenger of the Greek and Roman gods.

• The planet nearest the sun is named Mercury. It moves swiftly in its orbit like the messenger of the gods.

In astronomy, the planet closest to the sun, named after the fleet-footed messenger of the Roman gods (see under “Mythology and Folklore”) because of its swift movement in its orbit. Mercury takes only eighty-eight days to go around the sun. (See solar system.)

• Mercury is sometimes visible from the Earth as a morning or evening star.

In chemistry, a heavy, silvery metallic element, a liquid at normal temperatures. Mercury expands or contracts rapidly in response to changes in temperature and therefore was once widely used in thermometers.

• The term mercury is used figuratively in such expressions as “The mercury's rising” to mean that the temperature is going up.