Definitions for "Pentad"
Any element, atom, or radical, having a valence of five, or which can be combined with, substituted for, or compared with, five atoms of hydrogen or other monad; as, nitrogen is a pentad in the ammonium compounds.
Any grouping of five things.
Having the valence of a pentad.
Keywords:  cardinal, sum, four, number, one
the cardinal number that is the sum of four and one