isotherm vs isarithm

isotherm and isarithm both are nouns.

Word	Noun	Adjective	Verb	Adverb
isotherm	Yes	No	No	No
isarithm	Yes	No	No	No

As nouns, isarithm is a hypernym of isotherm; that is, isarithm is a word with a broader meaning than isotherm:

isotherm: (meteorology) an isogram connecting points having the same temperature at a given time
isarithm: a line drawn on a map connecting points having the same numerical value of some variable

Other hypernyms of isotherm include isogram, isopleth.

isotherm (noun)	isarithm (noun)
(meteorology) an isogram connecting points having the same temperature at a given time	a line drawn on a map connecting points having the same numerical value of some variable