·- A prefix, signifying twofold, double, twice.
II. Di- ·- denoting two atoms, radicals, groups, or equivalents, as the case may be. ·see Bi-, 2.
III. Di- ·- A prefix denoting through; also, between, apart, asunder, across. Before a vowel dia-becomes di-; as, diactinic; dielectric, ·etc.