sis Meaning, Definition & Usage

1. noun a female person who has the same parents as another person
   sister.
   
   • my sister married a musician
2. 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; Si; atomic number 14.
   
3. 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; SI; Systeme International d'Unites.
   
   • Today the United States is the only country in the world not totally committed to the Systeme International d'Unites
4. noun the syllable naming the seventh (subtonic) note of any musical scale in solmization
   si; te; ti.
   

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