The Monad in early Christian gnostic writings is an adaption of concepts of the Monad in Greek philosophy to Christian gnostic belief systems. The term monad comes from the Greek feminine noun monas (nominative singular, μονάς), "one unit," where the ending -s in the nominative form resolves to the ending -d in declination. This Monad is the spiritual source of everything which emanates the pleroma, and could be contrasted to the darkness of pure matter.