Bible Dictionaries
Pentad

Webster's Dictionary

(1):

(n.) 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.

(2):

(a.) Having the valence of a pentad.

Bibliography Information
Webster, Noah. Entry for 'Pentad'. Noah Webster's American Dictionary. https://www.studylight.org/​dictionaries/​eng/​web/​p/pentad.html. 1828.