PENTA-

Pen″ta– (?). [[Gr. πεντα-, a later combining form of πέντε five. See Five.]] 1. 1. A combining form denoting five; as, pentacapsular; pentagon.
2. 2. (Chem.) Denoting the degree of five, either as regards quality, property, or composition; as, pentasulphide; pentoxide, etc. Also used adjectively.