PENTA

Pen"ta-. Etym: [Gr. Five.]

1. A combining form denoting five; as, pentacapsular; pentagon.

2. (Chem.)

Definition: Denoting the degree of five, either as regards quality, property, or composition; as, pentasulphide; pentoxide, etc. Also used adjectively.

Source: Webster’s Unabridged Dictionary 1913 Edition