[ ahy-suh-thurm ]
/ ˈaɪ səˌθɜrm /


Meteorology. a line on a weather map or chart connecting points having equal temperature.
Also called isothermal line. Physics. a curve on which every point represents the same temperature.

Origin of isotherm

First recorded in 1855–60; back formation from isothermal Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for isotherm

British Dictionary definitions for isotherm


/ (ˈaɪsəʊˌθɜːm) /


a line on a map linking places of equal temperature
physics a curve on a graph that connects points of equal temperature
Also called: isothermal, isothermal line
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 isotherm



1860, from French isotherme (Humboldt, 1817), from Greek iso- (see iso-) + therme "heat" (see thermal).

Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for isotherm


[ īsə-thûrm′ ]

A line drawn on a weather map connecting points that have the same temperature. Each point can mark one temperature reading or an average of several readings.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.