What is the definition of fluorescence's?

Answer 1

A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite Mercury vapor. The excited Mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. I also put in the URL where I found the answer in case you would like to find out more about fluorescent lights.

http://en.wikipedia.org/wiki/Fluorescent_lights