[ law-guh-rith-uhm, -rith-, log-uh- ]
See synonyms for logarithm on Thesaurus.com
  1. the exponent of the power to which a base number must be raised to equal a given number; log: 2 is the logarithm of 100 to the base 10 (2 = log10 100).

Origin of logarithm

1605–15; <New Latin logarithmus<Greek lóg(os) log- + arithmós number; see arithmetic

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use logarithm in a sentence

  • She fidgeted, till Mr. Ernescliffe asked Norman if there was a table of logarithms in the house.

    The Daisy Chain | Charlotte Yonge
  • He left school at sixteen, after having mastered geometry and trigonometry, and having learned to use logarithms.

    Historic Fredericksburg | John T. Goolrick
  • This “Appendix” relates to logarithms and is an able document, containing several points of historical interest.

    William Oughtred | Florian Cajori
  • A great mathematical invention made by a Scotchman soon commanded his attention—the invention of logarithms.

    William Oughtred | Florian Cajori
  • The decimal point (or comma) was first used by the inventor of logarithms, John Napier, as early as 1616 and 1617.

    William Oughtred | Florian Cajori

British Dictionary definitions for logarithm


/ (ˈlɒɡəˌrɪðəm) /

  1. the exponent indicating the power to which a fixed number, the base, must be raised to obtain a given number or variable. It is used esp to simplify multiplication and division: if a x = M, then the logarithm of M to the base a (written log a M) is x: Often shortened to: log See also common logarithm, natural logarithm

Origin of logarithm

C17: from New Latin logarithmus, coined 1614 by John Napier, from Greek logos ratio, reckoning + arithmos number

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for logarithm


[ gə-rĭð′əm ]

  1. The power to which a base must be raised to produce a given number. For example, if the base is 10, then the logarithm of 1,000 (written log 1,000 or log10 1,000) is 3 because 103 = 1,000. See more at common logarithm natural logarithm.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.