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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

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Example Sentences

See Examples For:

si Si SI S.I.

Veteran Mexico goalkeeper Guillermo Ochoa posted a photo wearing a cowboy hat bearing the “¿Y si sí?” inscription.

From Los Angeles Times ● Jul. 5, 2026

It opens with a big-band cover of the 1920 standard “Whispering,” leading into the track, and closes with a reference to the 1947 French cabaret song “C’est si Bon.”

From The Wall Street Journal ● Jun. 15, 2026

In the city, the Queen was affectionately called si tau por, which means "boss lady" in Cantonese.

From BBC ● Sep. 14, 2022

In Spanish, Eso, si que es basically translates as "That's what it is!"

From Salon ● Nov. 8, 2021

For example, he chose the shapes D, R, b, h to represent the Cherokee syllables a, e, si, and ni, respectively, while the shape of the numeral 4 was borrowed for the syllable se.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

I saved up and bought a red 1989 Honda CRX Si.

From Los Angeles Times ● Jun. 22, 2026

To test the theory, Fang and Si conducted laboratory experiments using a thin layer of water driven by electromagnetic forces.

From Science Daily ● Jun. 3, 2026

He and his brother Si were close—but also very different, according to “Citizen Newhouse,” a book about the family by Carol Felsenthal.

From The Wall Street Journal ● May 27, 2026

The "Laudato Si" encyclical, which denounced mankind's ruthless exploitation of the environment, was hailed by experts for its scientific grounding.

From Barron's ● May 23, 2026

Princess Si Ling-chi was sitting under a mulberry tree when a silkworm cocoon fell into her teacup.

From "Middlesex: A Novel" by Jeffrey Eugenides

“I do like SI, because ‘artificial’ is not a very flattering thing.

From Salon ● Oct. 8, 2026

Clayton will chair the “Super Intelligence Force” which takes President Trump’s preferred name for AI: super intelligence or SI.

From The Wall Street Journal ● Oct. 3, 2026

“The Task Force shall act as a coordinating body to ensure that the U.S. remains at the forefront of SI development while protecting the American people,” the task force charter states.

From The Wall Street Journal ● Oct. 3, 2026

"Welcome to the new world of super intelligence - SI," he went on to say.

From BBC ● Sep. 22, 2026

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

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

“The joy of his life was his connection to the S.I. Newhouse School of Public Communications at Syracuse,” his son, Steven, said Tuesday.

From The Wall Street Journal ● May 27, 2026

According to a new survey titled “The American Journalist Under Attack,” released by Syracuse University’s S.I.

From Washington Times ● Dec. 30, 2023

Nearly half a century ago, Californians elected Republican S.I.

From Los Angeles Times ● Jul. 9, 2023

But he also edited The New Yorker for five years before departing over “conceptual differences” with publisher S.I.

From Seattle Times ● Jun. 14, 2023

"Thomas Grogan, Rockville, S.I., thirty-eight cents for coal, etc."

From Tom Grogan by Francis Hopkinson Smith

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