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.
Origin and Etymology of sidereal
Latin sidereus, from sider-, sidus star, constellation
First Known Use: 1647
Seen and Heard
What made you want to look up sidereal? Please tell us where you read or heard it (including the quote, if possible).