What is "zodi"

The zodi is a unit of zodiacal dust. One zodi is the amount of interplanetary dust in the inner solar system. This dust absorbs light from the Sun and re-radiates it as thermal radiation. The luminosity of the zodiacal dust in the Solar System is about 10 relative to the luminosity of the Sun, in The Astrophysical Journal, 713, p. 816 and in practice, this is the observable characteristic defining one zodi.