What is the meaning of sis?

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.
  • synonyms: silicon, Si, atomic number 14
• 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))
  • usage: "Today the United States is the only country in the world not totally committed to the Systeme International d'Unites"
  • synonyms: Systeme International d'Unites, Systeme International, SI system, SI, SI unit, International System of Units, International System
• The syllable naming the seventh (subtonic) note of any musical scale in solmization.
  • synonyms: ti, te, si
• A female person who has the same parents as another person.
  • usage: "my sister married a musician"
  • synonyms: sister