si

[ see ]

/ si /

Save This Word!

noun Music.

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

QUIZ

WILL YOU SAIL OR STUMBLE ON THESE GRAMMAR QUESTIONS?

Smoothly step over to these common grammar mistakes that trip many people up. Good luck!

Question 1 of 7

Fill in the blank: I can’t figure out _____ gave me this gift.

who

whom

TAKE THE QUIZ TO FIND OUT

Origin of si

First recorded in 1720–30; see origin at gamut

Words nearby si

shy away from, Shylock, Shymkent, shypoo, shyster, si, siabon, Siad Barre, sial, sialadenitis, sialagogic

Other definitions for si (2 of 4)

Symbol, Chemistry.

silicon.

Other definitions for si (3 of 4)

abbreviation

International System of Units.

Other definitions for si (4 of 4)

S.I.

abbreviation

Sandwich Islands.

Staten Island.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use si in a sentence

Last question: Who do you think is the sexiest SI swimsuit model of all time?
Anastasia Ashley, Surfer-Cum-Model, Rides The Viral Internet Wave|James Joiner|December 23, 2014|DAILY BEAST
Except for nine of them are musical words: do, re, mi, fa, so, la, ti—and si—are musical.
Well, La Ti Da: Stephin Merritt’s Winning Little Words of Scrabble|David Bukszpan|October 11, 2014|DAILY BEAST
Michael Sam has one big advantage over the aging NFL execs who whined to SI.
Michael Sam Is Not a ‘Distraction’|Dave Cullen|February 12, 2014|DAILY BEAST
It was the only SI story Shrake ever wrote that the magazine would not print and Laguerre was embarrassed.
‘The Land of the Permanent Wave’ Is Bud Shrake’s Classic Take on ‘60s Texas|Edwin Shrake|February 2, 2014|DAILY BEAST

Raymond Depardon: Un Moment Si Doux is on display at Grand Palais, Paris until February 10, 2014.
Photographer Raymond Depardon Captures the ‘Sweet Moments’|Sarah Moroz|November 15, 2013|DAILY BEAST
Ils me respondirent que si je la voulois, ils me la donnoyent tout faict.
The Jesuit Relations and Allied Documents, Vol. II: Acadia, 1612-1614|Various
Il prenoit des symptomes si mortels, que souvent nous n'attendions sinon qu'il nous demeurast entre les mains.
The Jesuit Relations and Allied Documents, Vol. II: Acadia, 1612-1614|Various
De moi, je ne say qu'en dire, d'autant que je ne veux affirmer ny le si ny le non en ce dont je n'ay vidence.
The Jesuit Relations and Allied Documents, Vol. II: Acadia, 1612-1614|Various
La rougeur estoit si esclatante, que toute la rivire s'en teingnoit et en reluysoit.
The Jesuit Relations and Allied Documents, Vol. II: Acadia, 1612-1614|Various
Or ne say-je quelle estoit sa maladie; si elle venoit seulement par intervalles, ou non, je n'en say rien: tant y a que le 2.
The Jesuit Relations and Allied Documents, Vol. II: Acadia, 1612-1614|Various

British Dictionary definitions for si (1 of 5)

si¹

/ (siː) /

noun

music a variant of te

British Dictionary definitions for si (2 of 5)

si²

the internet domain name for

Slovenia

British Dictionary definitions for si (3 of 5)

Si¹

Si Kiang

/ (ʃiː) /

noun

a variant transliteration of the Chinese name for the Xi

British Dictionary definitions for si (4 of 5)

Si²

the chemical symbol for

silicon

British Dictionary definitions for si (5 of 5)

symbol for

Système International (d'Unités)See SI unit

abbreviation for

NZ South Island

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for si

The symbol for silicon.