Earth & SkyGreek → English
Isotherm
/ˈaɪsoʊθɜːrm/noun
A line on a map or chart joining points of the same temperature.
The Greek roots
ἴσος
ísos
equal, same
θέρμη
thérmē
heat
Literally: “equal heat”
The story of the word
Alexander von Humboldt drew the first isothermal lines in 1817, joining places of equal mean temperature and inventing at a stroke the way climate would be pictured ever after. Every relative on the weather map follows his template: isobars for pressure, isohyets for rainfall, isohels for sunshine. The ἴσος half also underwrites isosceles and isotope, and the θέρμη half heats the thermos flask.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 19th century
Same family
isobarthermometerthermalisotopeisohyet
In a sentence
The ten-degree isotherm has shifted about a hundred kilometres north since the survey began.