1. The SI unit of illuminance, symbol lx, equal to one lumen per metre squared. The plural is unchanged lux.

Average light intensities are, very roughly:

  • 100 lx inside a house
  • 300 ~ 500 lx in a workplace
  • 2 000 lx outside on a dull winter's day
  • 10 000 lx outside on a bright summer's day
The eyes adjust so that the difference in illuminance does not seem so enormous; also (thanks, Oolong) illuminance is perceived logarithmically.

2. A brand of soap. (You knew that.)