Dictionary entry

Dia-

Webster's Dictionary 1913

{ Di″a– (?), Di– }. [Gr. διά 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.