si·​de·​re·​al | \ sī-ˈdir-ē-əl How to pronounce sidereal (audio) , sə- \

Definition of sidereal

: of, relating to, or expressed in relation to stars or constellations : astral

Examples of sidereal in a Sentence

Recent Examples on the Web Called sidereal time, the measurement calculates the length of a day by comparing the earth's rotation to the stars. Aaron Pressman, Fortune, 12 Apr. 2017 One tweet, in particular, has birthed a fair number of inky astronauts floating across a sidereal arm. Jesse Lichtenstein, New York Times, 15 June 2017 With this definition, a sidereal year is something like 365.256363 solar days. Rhett Allain, WIRED, 29 Feb. 2012

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.

See More

First Known Use of sidereal

1612, in the meaning defined above

History and Etymology for sidereal

Latin sidereus, from sider-, sidus star, constellation

Keep scrolling for more

Learn More About sidereal

Time Traveler for sidereal

Time Traveler

The first known use of sidereal was in 1612

See more words from the same year

Listen to Our Podcast About sidereal

Dictionary Entries Near sidereal



sidereal astronomy

See More Nearby Entries 

Statistics for sidereal

Cite this Entry

“Sidereal.” Dictionary, Merriam-Webster, Accessed 19 Sep. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon


Test Your Vocabulary

Difficult Spelling Words Quiz

  • alphabet pasta spelling help
  • Which is the correct spelling?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!