DI-

a prefix, signifying twofold, double, twice.

2. di- ·- denoting two atoms, radicals, groups, or equivalents, as the case may be. ·see bi-, 2.

3. di- ·- a prefix denoting through; also, between, apart, asunder, across. before a vowel dia-becomes di-; as, diactinic; dielectric, ·etc.