sunspot number

noun

Definition of sunspot number

: an arbitrary numerical value that is used to describe the sun's spottedness, is the number of individual spots plus 10 times the number of disturbed regions, and depends upon the instrumental equipment and personal equation of the observer

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

  • More than 250,000 words that aren't in our free dictionary
  • Expanded definitions, etymologies, and usage notes
  • Advanced search features
  • Ad free!

Learn More About sunspot number

Statistics for sunspot number

Cite this Entry

“Sunspot number.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sunspot%20number. Accessed 23 Jun. 2021.

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

WORD OF THE DAY

Test Your Vocabulary

Return of Name that Color!

  • a light greenish blue color
  • Name that color:
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
Typeshift

Anagram puzzles meet word search.

TAKE THE QUIZ
Love words? Need even more definitions?

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