[ ok-teyn ]
/ ˈɒk teɪn /

noun Chemistry.

any of 18 isomeric saturated hydrocarbons having the formula C8H18, some of which are obtained in the distillation and cracking of petroleum.

Nearby words

  1. octamer,
  2. octamerous,
  3. octameter,
  4. octan,
  5. octandrious,
  6. octane number,
  7. octanedioic acid,
  8. octangle,
  9. octangular,
  10. octanoic acid

Origin of octane

First recorded in 1870–75; oct- + -ane

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for octane

British Dictionary definitions for octane


/ (ˈɒkteɪn) /


a liquid alkane hydrocarbon found in petroleum and existing in 18 isomeric forms, esp the isomer n -octane. Formula: C 8 H 18See also isooctane
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

Word Origin and History for octane



hydrocarbon of the methane series, 1872, coined from octo- (see octa-) + -ane; so called because it has eight carbon atoms. A fuel's octane rating, in reference to its anti-knocking quality, is attested from 1932.

Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for octane


[ ŏktān′ ]

Any of several hydrocarbons having eight carbon atoms connected by single bonds. It is commonly added to gasoline to prevent knocking from uneven burning of fuel in internal-combustion engines. Octane is the eighth member of the alkane series. Chemical formula: C8H18.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.