Webster's Revised Unabridged Dictionary · 1913

Monad

Monad , noun

[Latin monas, -adis, a unit, Greek {not transcribed}, {not transcribed}, from mo`nos alone.]

1.
An ultimate atom, or simple, unextended point; something ultimate and indivisible.
2.
(Philosophy of Leibnitz) The elementary and indestructible units which were conceived of as endowed with the power to produce all the changes they undergo, and thus determine all physical and spiritual phenomena.
3.
(Zoology) One of the smallest flagellate Infusoria; esp., the species of the genus Monas, and allied genera.
4.
(Biology) A simple, minute organism; a primary cell, germ, or plastid.
5.
(Chemistry) An atom or radical whose valence is one, or which can combine with, be replaced by, or exchanged for, one atom of hydrogen.
Collocations (1)
Monad deme (Biology) , in tectology, a unit of the first order of individuality.