[1] : The Collaborative International Dictionary of English v.0.48

penta- \pen"ta-\, pref. gr. penta-, a later combining form of
   pe`nte five. see five.
   1. a combining form denoting five; as, pentacapsular;
      pentagon.
      1913 webster

   2. chem. denoting the degree of five, either as regards
      quality, property, or composition; as, pentasulphide,
      containing five sulfur atoms; pentoxide, containing five
      oxygen atoms, etc. also used adjectively.
      1913 webster
see also:
five 

Penta- >> P Words
Penta-, definition of term: Penta-
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