Re: What does the SI on a floresent light bulb mean?

The SI printed on a fluorescent bulb signifies that the system of measurement used was the modern metric system. The unit of measurement used to quantify luminous intensity is the candela. Here are two links that explain the SI system of measurement and define the candela:

http://physics.nist.gov/cuu/Units/introduction.html
http://physics.nist.gov/cuu/Units/candela.html