si

noun

another term for ti.

early 18th century: from the initial letters of Sancte Iohannes, the closing words of a Latin hymn (see solmization).

symbol

the chemical element silicon.

abbreviation, noun

the international system of units of measurement.

from French Système International .

abbreviation

statutory instrument.

noun, symbol

the chemical element of atomic number 14, a non-metal with semiconducting properties, used in making electronic circuits. Pure silicon exists in a shiny dark grey crystalline form and as an amorphous powder.

early 19th century: alteration of earlier silicium, from Latin silex, silic- ‘flint’, on the pattern of carbon and boron .