iono-comb. form

Stress is usually determined by a subsequent element and vowels may be reduced accordingly.
Origin: Formed within English, by compounding. Etymons: ion n., -o- connective.
Etymology: < ion n. + -o- connective. Compare German Iono- (formations in which are found from at least the end of the 19th cent.).Attested earliest at the beginning of the 20th cent., earliest in ionogen n., perhaps after a German model. Combining with second elements ultimately of Greek or Latin origin.
This entry has been updated (OED Third Edition, March 2012; most recently modified version published online January 2018).