From WordNet (r) 3.0 (2006):
Si
n 1: a tetravalent nonmetallic element; next to oxygen it is the
most abundant element in the earth's crust; occurs in clay
and feldspar and granite and quartz and sand; used as a
semiconductor in transistors [syn: silicon, Si, atomic
number 14]
2: a complete metric system of units of measurement for
scientists; fundamental quantities are length (meter) and
mass (kilogram) and time (second) and electric current
(ampere) and temperature (kelvin) and amount of matter (mole)
and luminous intensity (candela); "Today the United States is
the only country in the world not totally committed to the
Systeme International d'Unites" [syn: Systeme International
d'Unites, Systeme International, SI system, SI, SI
unit, International System of Units, International
System]
3: the syllable naming the seventh (subtonic) note of any
musical scale in solmization [syn: ti, te, si]