Editing Contour line (section)

==== Temperature and related subjects ====
[[Image:arctic.svg|thumb|The {{convert|10|C}} mean isotherm in July, marked by the red line, is commonly used to define the border of the [[Arctic region]]]]

An '''isotherm''' ({{ety|grc|''θέρμη'' (thermē)|heat}}) is a line that connects points on a map that have the same [[temperature]]. Therefore, all points through which an isotherm passes have the same or equal temperatures at the time indicated.<ref name="DataAir">{{cite web|author=DataStreme Atmosphere|publisher=American Meteorological Society|url=http://www.ametsoc.org/amsedu/dstreme/learn/sample.act.html |title=Air Temperature Patterns|date=2008-04-28|access-date=2010-02-07 |archive-url = https://web.archive.org/web/20080511124504/http://www.ametsoc.org/amsedu/dstreme/learn/sample.act.html |archive-date = 2008-05-11}}</ref><ref name="Hughes"/>  An isotherm at 0&nbsp;°C is called the [[freezing level]]. The term ''lignes isothermes'' (or ''lignes d'égale chaleur)'' was coined by the [[Prussia]]n geographer and naturalist [[Alexander von Humboldt]], who as part of his research into the geographical distribution of plants published the first map of isotherms in Paris, in 1817.<ref>{{ cite book | last=Daum | first=Andreas W.|author-link=Andreas Daum | year=2024 | title=Alexander von Humboldt: A Concise Biography | location=Trans. Robert Savage. Princeton, N.J. | publisher=Princeton University Press |pages=106–107 | isbn=978-0-691-24736-6 }}</ref><ref>{{Cite journal|last=Munzar|first=Jan|date=1967-09-01|title=Alexander Von Humboldt and His Isotherms|journal=Weather|language=en|volume=22|issue=9|pages=360–363|doi=10.1002/j.1477-8696.1967.tb02989.x|issn=1477-8696|bibcode=1967Wthr...22..360M}}</ref> According to Thomas Hankins, the Scottish engineer [[William Playfair]]'s graphical developments greatly influenced Alexander von Humbolt's invention of the isotherm.<ref>{{Cite journal |date=1999 |title=Blood, Dirt, and Nomograms: A Particular History of Graphs |url=https://www.journals.uchicago.edu/doi/10.1086/384241 |journal=Isis |language=en |volume=90 |issue=1 |pages=50–80 |doi=10.1086/384241 |issn=0021-1753}}</ref> Humbolt later used his visualizations and analyses to contradict theories by Kant and other Enlightenment thinkers that non-Europeans were inferior due to their climate.<ref>{{Cite journal |last=Strobl |first=Michael |date=2021 |title=Alexander von Humbolt's Climatological Writings |url=https://onlinelibrary.wiley.com/doi/10.1111/glal.12313 |journal=German Life and Letters |language=en |volume=74 |issue=3 |pages=371–393 |doi=10.1111/glal.12313 |issn=0016-8777}}</ref> 

An '''isocheim''' is a line of equal mean winter temperature, and an '''isothere''' is a line of equal mean summer temperature.

An '''isohel''' ({{langx|grc|ἥλιος|helios|Sun|label=none}}) is a line of equal or constant [[solar radiation]].

An '''isogeotherm''' is a line of equal temperature beneath the Earth's surface.