iso- (English)

Where does "iso-" come from?

The English prefix 'iso-' is a learned borrowing from the Ancient Greek word 'ísos', meaning 'equal'. Its ultimate origins are highly debated among linguists, with theories tracing it back to Proto-Indo-European roots connected to concepts like 'seeing', 'separation', or even numerical references to 'two'. Today, it functions as a versatile scientific prefix used to denote identity, equality, or structural similarity.

Full etymology tree

• iso- (English), 'Same, identical.'
  • learned borrowing ἴσος (ísos) (Ancient Greek), 'equal (to), equivalent (to), consistent (to), agreement (to)'
    • inherited ἶσος (îsos) (Ancient Greek), 'Epic form of ἴσος (ísos)'
    • inherited *weyd- (Proto-Indo-European), 'to see'
    • inherited *wi- (Proto-Indo-European)

Direct ancestors

• ἴσος (Ancient Greek)

Updated June 2026

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