- 1. Two, twice. 2. In chemistry, often used in place of bis- when not likely to be confusing; e.g., dichloro- compounds. Cf.:bi-, bis-. [G. dis, two]
* * *prefix denotingtwo or double.
* * *[Gr. dis twice] a prefix meaning twice. In chemical nomenclature, the use of di- is preferred to the use of bi- (q.v.).
Medical dictionary. 2011.