iso- (English)
Where does "iso-" come from?
The English prefix 'iso-', used in technical terms meaning 'same' or 'equal', is an internationalism adopted as a learned borrowing from the Ancient Greek word 'ἴσος' ('ísos'), meaning 'equal'[1]. In earlier Greek dialects, the word appears as '*ϝῖσϝος' ('*wîswos')[2]. Linguists trace this Greek form back to Proto-Hellenic '*wíswos', though its deeper ancestry remains unsettled, with proposals linking it either to a Proto-Indo-European root for separation '*wi-' or to '*weyd-', meaning 'to see' or 'know'[2].
Open questions
- The deeper Proto-Indo-European origin of the Ancient Greek root is disputed, with competing proposals deriving it from roots meaning to separate, to see, or from the numeral two. [2]
- Linguist Robert Beekes rejects the derivation from Proto-Indo-European '*wi-' because the affix '*-su-' was apparently not preserved in Greek. [2]
- The Proto-Indo-European root '*wí' is itself tentatively reconstructed as deriving from '*dwi-' via the loss of the initial consonant or through the Kortlandt effect. [3]
Full etymology tree
- iso- (English), 'Same, identical.'
- learned borrowing ἴσος (ísos) (Ancient Greek), 'equal (to), equivalent (to), consistent (to), agreement (to)'
- derived ἶσος (îsos) (Ancient Greek), 'Epic form of ἴσος (ísos)'
- derived *ϝῖσϝος (*wîswos) (Ancient Greek)
- derived ἶσος (îsos) (Ancient Greek), 'Epic form of ἴσος (ísos)'
- learned borrowing ἴσος (ísos) (Ancient Greek), 'equal (to), equivalent (to), consistent (to), agreement (to)'
Ancestors
- ἴσος (Ancient Greek)
Descendants and derived words
- anteiso- (English)
- isolatitude (English)
Sources
- iso- (English) - Wiktionary
- ἴσος (ísos) (Ancient Greek) - Wiktionary
- wí (Proto-Indo-European) - Wiktionary
Updated September 2026
Etymology data from Wiktionary, CC BY-SA 4.0 · About Miraris