Definition of sidereal
: of, relating to, or expressed in relation to stars or constellations : astral
sidereal was our Word of the Day on 03/30/2016. Hear the podcast!
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Recent Examples of sidereal from the Web
One tweet, in particular, has birthed a fair number of inky astronauts floating across a sidereal arm.
With this definition, a sidereal year is something like 365.256363 solar days.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'sidereal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Mark Time With the History of sidereal
In Latin, the word for a star or constellation 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 documented in English in 1642. 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: 1612See Words from the same year
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