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

Un día después de cumplir 40 años, McVay entrenó como si ya no fuera el niño prodigio, sino un líder envejecido que se expone a las críticas.

From Los Angeles Times • Jan. 26, 2026

Jesus showed himself to the disciples, In quel tempo, quando si fu manifesta -

From BBC • Apr. 25, 2025

Pero si es electa, promete aumentar el gasto público y privado en investigación.

From Science Magazine • May 8, 2024

“Vacúnate como regalo de Año Nuevo si aún no lo has hecho”, dijo Schaffner.

From New York Times • Dec. 31, 2023

“It’s called ‘Por si acaso no regreso,’ and it’s about Celia realizing she might never be able to see Cuba again.

From "Across So Many Seas" by Ruth Behar