si

1 of 3

noun

ˈsē

: ti entry 1

Si

2 of 3

symbol

silicon

SI

3 of 3

abbreviation

International System of Units

Word History

Etymology

Noun

Italian

Abbreviation

French Système International d'Unités

First Known Use

Noun

1728, in the meaning defined above

Time Traveler

The first known use of si was in 1728

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SI

si

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Cite this Entry

Style

“Si.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/si. Accessed 14 Jul. 2025.

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Kids Definition

si

noun

ˈsē

: the seventh note of a scale : ti

Medical Definition

Si

1 of 2 symbol

silicon

SI

2 of 2 abbreviation

International System of Units

Etymology

Abbreviation

French Système International d'Unités

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si

noun

symbol

abbreviation

Word History

Browse Nearby Words

Cite this Entry

Kids Definition

Medical Definition