Word of the Day

: March 21, 2007

sidereal

adjective sye-DEER-ee-ul

What It Means

1 : of or relating to stars or constellations

2 : measured by the apparent motion of the stars

sidereal in Context

Few astronomers have witnessed the sidereal phenomenon of a supernova.

Did You Know?

In Latin, the word for "heavenly body" is "sidus." Latin speakers used that word to form "desiderare" ("from a heavenly body") and "considerare" ("to think about a heavenly body"), which were adopted into English as "desire" and "consider." "Sidereal," another "sidus" creation, was first used in English in 1647. Thirty-four years later, an astronomer coined the phrase "sidereal year" for the time in which the earth completes one revolution in its orbit around the sun, measured with respect to the fixed stars. Not surprisingly, other sidereal measurements of time followed, including the sidereal month, the sidereal day, the sidereal hour, and even the sidereal minute.

*Indicates the sense illustrated by the example sentence.