si Meaning, Definition & Usage

  1. noun 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
    silicon; atomic number 14.
  2. noun 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)
    Systeme International; SI unit; SI system; International System of Units; International System; Systeme International d'Unites.
    • Today the United States is the only country in the world not totally committed to the Systeme International d'Unites
  3. noun the syllable naming the seventh (subtonic) note of any musical scale in solmization
    te; ti.

WordNet


Si
Etymology
It.
Definitions
  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. now called ti

Webster 1913