Diathermanity

Part of speech: noun

Definitions

1. The property of a material that allows radiant heat, such as infrared radiation, to pass straight through it without being absorbed
2. The ability of a medium to let thermal radiation travel across it, a measure of how transparent it is to heat rays
3. How readily a body or substance permits radiant heat to traverse it unabsorbed, a quality opposite to opacity for warmth

Etymology: Diathermanity is the property of a substance that lets radiant heat pass through it, and the word was built in the 19th century from Greek parts rather than handed down from antiquity. Its first element is "dia-", meaning "through," and the second is "thermansis," from "therme," meaning "heat," a form tied to the same root as "thermos" and "thermometer." Physicists needed a name for the quality that makes glass transparent to heat from a sun but opaque to the radiation of a warm room, and they assembled one from classical building blocks. The coinage is a close relative of "diathermic" and "diathermy," the latter a medical term for heating body tissue with electric currents. The English adjective "diathermanous," meaning heat-transmitting, appeared earlier in the 1800s, and the noun followed the same pattern. Scholars sometimes used the word to contrast heat-passing bodies with "athermanous" ones, which block radiant heat, so the pair marks a clean division between materials that let warmth through and those that stop it.

Synonyms: diathermancy

Antonyms: athermancy