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.
A group of five. In climatology, it is applied to a period of five consecutive days. It is often preferred to the week for climatological purposes since it is an exact factor of the 365-day year.
A method of exploring a subject. The pentad considers the five dramatic aspects: the act, the actor, the scene, the agency (means), and the purpose (reason).