The Monad in early Christian gnostic writings is an adaptation 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 declension.
In some gnostic systems the Supreme Being is known as the Monad, the One, The Absolute Aiōn teleos (The Perfect Aeon, αἰών τέλεος), Bythos (Depth or Profundity, Βυθός), Proarchē (Before the Beginning, προαρχή), and Hē Archē (The Beginning, ἡ ἀρχή) and The ineffable parent. The One is the high source of the pleroma, the region of light. The various emanations of The One are called Aeons.
According to Theodoret's book on heresies (Haereticarum Fabularum Compendium i.18) the Arab Christian Monoimus (150-210) used the term Monad to mean the highest god which created lesser gods, or elements (similar to Aeons). In some versions of Christian gnosticism, especially those deriving from Valentinius, a lesser deity known as the Demiurge had a role in the creation of the material world in addition to the role of the Monad. In these forms of gnosticism, the God of the Old Testament is often considered to have been the Demiurge, not the Monad, or sometimes different passages are interpreted as referring to each.
According to Hippolytus, this view was inspired by the Pythagoreans, for whom the first thing that came into existence was referred to as the Monad, which begat the dyad, which begat the numbers, which begat the point, begetting lines, etc.Pythagorean and Platonic philosophers like Plotinus and Porphyry condemned "Gnosis" that would later characterize Gnosticism (see Neoplatonism and Gnosticism) for their treatment of the monad or one.