- a prefix occurring in loanwords from Greek, where it meant “two,” “twice,” “double” (diphthong); on this model, freely used in the formation of compound words (dicotyledon; dipolar) and in chemical terms (diatomic; disulfide).
Origin of di-1
- variant of dis-1 before b, d, l, m, n, r, s, v, and sometimes g and j: digest; divide.
- variant of dia- before a vowel: diorama.
- twice; two; doubledicotyledon
- containing two specified atoms or groups of atomsdimethyl ether; carbon dioxide
- a nontechnical equivalent of bi- 1 (def. 5c)
- variant of dia- diopter
Word Origin and History for di-
word-forming element meaning "two, double, twice," from Greek di-, from dis "twice," related to duo (see two).
word-forming element meaning "apart, asunder," form of dis- before certain voiced consonants.
word-forming element meaning "through; thoroughly," form of dia- before vowels.
- Two; twice; double:dichromatic.
- Containing two atoms, radicals, or groups:diiodide.
- A prefix that means two, twice, or double. It is used commonly in chemistry, as in dioxide, a compound having two oxygen atoms.