资料来源 : Webster's Revised Unabridged Dictionary (1913)

Di- \Di-\ [Gr. di`s- twice; akin to ? two, L. bis twice. See
   {Two}, and cf. {Bi-}, {Dia-}. The L. pref. dis- sometimes
   assumes the form di-. See {Dis-}.]
   A prefix, signifying twofold, double, twice; (Chem.) denoting
   two atoms, radicals, groups, or equivalents, as the case may
   be. See {Bi-}, 2.

Dia- \Di"a-\, Di- \Di-\ . [Gr. dia` through; orig., dividing
   into two parts; akin to ? two. See {Two}, and cf. 1st {Di-}.]
   A prefix denoting through; also, between, apart, asunder,
   across. Before a vowel dia-becomes di-; as, diactinic;
   dielectric, etc.