exa- (English)

Where does "exa-" come from?

The English prefix 'exa-' originates from the Ancient Greek word 'héx' meaning 'six'[1]. It was coined as a metric prefix to denote the sixth order of 10 to the third power, following an analogy established by 'tera-'[1]. The Greek term 'héx' itself traces back to the Proto-Hellenic form '*hwéks' and further to the Proto-Indo-European root '*swéḱs'[2].

Open questions

• The derivation from the Proto-Hellenic form '*hwéks' and the Proto-Indo-European root '*swéḱs' represents a linguistic reconstruction rather than a directly attested form. [2]

Full etymology tree

• exa- (English), 'In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10¹⁸ (a short scale quintillion or long scale trillion).'
  • derived ἕξ (héx) (Ancient Greek), 'six'
    • inherited *hwéks (Proto-Hellenic), 'six'
      • inherited *swéḱs (Proto-Indo-European), 'six'

Descendants and derived words

• exbi- (English)

Sources

1. exa- (English) - Wiktionary
2. ἕξ (héx) (Ancient Greek) - Wiktionary

Updated August 2026

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