Noun has 3 senses

• si(n = noun.substance) atomic number 14, silicon - 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;



• si(n = noun.quantity) international system, international system of units, si system, si unit, systeme international, systeme international d'unites - 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"


• si(n = noun.communication) te, ti - the syllable naming the seventh (subtonic) note of any musical scale in solmization;