Si

1.

(Mus.) A syllable applied, in solmization, to the note B; more recently, to the seventh tone of any major diatonic scale. It was added to Guido's scale by Le Maire about the end of the 17th century.

Noun	1.	SI - 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" Synonyms: International System, International System of Units, SI system, Systeme International, Systeme International d'Unites
	2.	Si - 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 Synonyms: atomic number 14, silicon
	3.	si - the syllable naming the seventh (subtonic) note of any musical scale in solmization Synonyms: te, ti

1.	(unit)	SI - Système International.
2.	(character)	SI - Shift In.
3.	(networking)	si - The country code for Slovenia.

System Informationatomic number 14, chemical element, clay, element, feldspar, felspar, granite, quartz, sand, semiconducting material, semiconductor, silicon, silicone, silicone polymer