An Etymological Dictionary of Astronomy and Astrophysics

A unit of → energy in the → International System of Units equal to the → work performed by one → newton over a distance of 1 → meter.
1 J is equivalent to 10⁷ ergs = 1 Watt second =
2.78 &times 10^-7 kWh = 0.2389 calories =
6.24 × 10¹⁸ eV.

Etymology (EN): In honor of the English physicist James Prescott Joule (1818-1889), who established that the various forms of energy (mechanical, electrical, and heat) are basically the same and can be changed, one into another.

Etymology (PE): Joule is in Pers. pronounced as žul, loaned from the Fr. rendering of the E. name.