From Latin monas, “unity; a unit” and Greek monas "unit," from monos "alone."
In general use in the gnostic teachings, the Monad refers to the Being, the Innermost, our own inner Spirit. In Kabbalah, the Monad is represented by the sephiroth Chesed, Geburah, and Tiphereth. In Sanskrit, this corresponds to Atman-Buddhi-Manas.
"The God of Pythagoras was the Monad, or the One that is Everything. He described God as the Supreme Mind distributed throughout all parts of the universe--the Cause of all things, the Intelligence of all things, and the Power within all things. He further declared the motion of God to be circular, the body of God to be composed of the substance of light, and the nature of God to be composed of the substance of truth." - Manly P. Hall
"We must distinguish between Monads and Souls. A Monad, in other words, a Spirit, is; a Soul is acquired. Distinguish between the Monad of a world and the Soul of a world; between the Monad of a human and the Soul of a human; between the Monad of an ant and the Soul of an ant. The human organism, in final synthesis, is constituted by billions and trillions of infinitesimal Monads. There are several types and orders of primary elements of all existence, of every organism, in the manner of germs of all the phenomena of nature; we can call the latter Monads, employing the term of Leibnitz, in the absence of a more descriptive term to indicate the simplicity of the simplest existence. An atom, as a vehicle of action, corresponds to each of these genii or Monads. The Monads attract each other, combine, transform themselves, giving form to every organism, world, micro-organism, etc. Hierarchies exist among the Monads; the Inferior Monads must obey the Superior ones that is the Law. Inferior Monads belong to the Superior ones. All the trillions of Monads that animate the human organism have to obey the owner, the chief, the Principal Monad. The regulating Monad, the Primordial Monad permits the activity of all of its subordinates inside the human organism, until the time indicated by the Law of Karma." - Samael Aun Weor, The Esoteric Treatise of Hermetic Astrology
“(The number) one is the Monad, the Unity, Iod-Heve or Jehovah, the Father who is in secret. It is the Divine Triad that is not incarnated within a Master who has not killed the ego. He is Osiris, the same God, the Word.” - Samael Aun Weor, Tarot and Kabbalah
“When spoken of, the Monad is referred to as Osiris. He is the one that has to Self-realize Himself... Our own particular Monad needs us and we need it. Once, while speaking with my Monad, my Monad told me, ‘I am self-realizing Thee; what I am doing, I am doing for Thee.’ Otherwise, why are we living? The Monad wants to Self-realize and that is why we are here. This is our objective.” - Samael Aun Weor, Tarot and Kabbalah
"The Monads or Vital Genii are not exclusive to the physical organism; within the atoms of the Internal Bodies there are found imprisoned many orders and categories of living Monads. The existence of any physical or suprasensible, Angelic or Diabolical, Solar or Lunar body, has billions and trillions of Monads as their foundation." - Samael Aun Weor, The Esoteric Treatise of Hermetic Astrology