[codefox1]

International System of Units aka SI.

The seven SI base units : kelvin (temperature), second (time), metre (length), kilogram (mass), candela (luminous intensity), mole (amount of substance) and ampere (electric current). Tons of (useful?) info on the net.

(I didn't know what it meant either@)

[morzh]

SI is System International.

http://en.wikipedia.org/wiki/Internation...m_of_Units

It is pretty much a standard system of units used in physics.
Not all physicists like SI, some still prefer CGS (centimeter-gram-second), which derivatives, CGSE (electrical) and CGSM (magnetic) are popular in electricity/magnetism books.
For example, a unit of force in SI is "Newton" (roughly 1/10 of a kilo) but in CGS it is "dyne" which is 1/100,000 of Newton.
or unit of energy: in SI it is a "Joule" and in CGS it is an "erg" which is 1/10,000,000 of "joule".