si (Latin)

Where does "si" come from?

The Latin conjunction 'si', meaning 'if' or 'supposing that'[1], descends from the Proto-Italic form '*sei'[1][3]. This Italic term originated as an innovated thematic locative singular of the Proto-Indo-European demonstrative '*só'[3], meaning 'this' or 'that'[1][2], with a primitive sense of 'so, thus' used in parataxis through the intermediate notion of 'in this'[1]. This older demonstrative background is also preserved in the Latin word 'sīc'[1].

Open questions

• The derivation of the Proto-Italic locative from the Proto-Indo-European demonstrative relies on reconstructed forms. [1] [3]

Full etymology tree

• si (Latin), 'if, supposing that'
  • inherited *sei (Proto-Italic), 'thus, so'
    • derived *só (Proto-Indo-European), 'this'

Ancestors

• *sei (Proto-Italic)
• *só (Proto-Indo-European)

Cognates and doublets

• sic (Latin)

Descendants and derived words

• si (Catalan)
• si (Catalan)
• si (Catalan)
• si (Catalan)
• se (Franco-Provençal)
• si (French)
• si (French)
• si (French)
• si (French)
• se (Galician)
• se (Galician)
• se (Italian)

Sources

1. si (Latin) - Wiktionary
2. só (Proto-Indo-European) - Wiktionary
3. sei (Proto-Italic) - Wiktionary

Updated October 2026

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Etymology data from Wiktionary, CC BY-SA 4.0 · About Miraris