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• si
  si

  noun

  the syllable used for the seventh tone of a scale and sometimes for the tone B.
• Si
  Si

  silicon.
• SI
  SI

  abbreviation

  International System of Units.
• S.I.
  S.I.

  abbreviation

  Sandwich Islands.

si

¹ American  

[see] / si /

noun

Music.

1. the syllable used for the seventh tone of a scale and sometimes for the tone B.

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Si ² American  

Symbol, Chemistry.

1. silicon.

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SI ³ American  

abbreviation

1. International System of Units.

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S.I. ⁴ American  

abbreviation

1. Sandwich Islands.

2. Staten Island.

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SI ¹ British  

symbol

1. Système International (d'Unités) See SI unit

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abbreviation

1. South Island

Si ² British  

/ ʃiː /

noun

1. a variant transliteration of the Chinese name for the Xi

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Si ³ British  

symbol

1. silicon

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si ⁴ British  

/ siː /

noun

1. music a variant of te

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si ⁵ British  

abbreviation

1. Slovenia

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Etymology

Origin of si

First recorded in 1720–30; see origin at gamut

Example Sentences

The painting, which came from the private collection of media magnate SI Newhouse, is also now the fourth most expensive artwork ever sold at auction, according to ARTnews.

From BBC • May 19, 2026

About 140 graves sit on the west side of the graveyard and 138 that sit on the opposite site, according to a satellite image taken in early April provided by SI Analytics.

From BBC • May 7, 2026

The memorial itself holds a "tiered system of commemoration", says Korean research company SI Analytics.

From BBC • May 7, 2026

In 2023, Authentic put the SI name on Lunatix, a sputtering ticket marketplace.

From Los Angeles Times • Apr. 5, 2026

Oct-ober SI “Did you give Tony my thank-you note?”

From "The Dead and the Gone" by Susan Beth Pfeffer