Krypton

Krypton is a stable noble gas. It has an atomic number of 36. The name krypton comes from the Greek word kryptos meaning hidden. It is used in fluorescent lamps, flashbulbs, and as a wavelength standard. The metre used to be defined as 1,650,763.73 wavelengths in a vacuum of krypton gas.^[1]

The Simple English Wiktionary has a definition for: krypton.

1. ↑ "WebElements Periodic Table of the Elements". webelements.com. 2011. Retrieved 17 June 2011.