Etymology From Ancient Greek ἐννεάς (enneás), ἐννεάδος (enneádos, “body of nine”) + -ad (suffix designating a unit); analysable as ennea- + -ad. The Greek words ἐννεάς and ἐννεάδος are derived from ἐννέᾰ (ennéă, “nine”) (ultimately from Proto-Indo-European *h₁néwn̥ (“nine”)) + -ᾰ́ς (-ắs, suffix forming abstract nouns of number from numerals) or -ος (-os).
The ennead, according to the Pythagoreans, circulates all numbers within itself, and there can be no number beyond it. For the natural progression of numbers is as far as to 9, but after it their retrogression takes place. For 10 becomes as it were again the monad. […] Hence it is not possible there should be any elementary number beyond the ennead.1816, Proclus, chapter XXXI, in Thomas Taylor, transl., The Six Books of Proclus the Platonic Successor, on the Theology of Plato, Translated from the Greek; […] Two Volumes, volume II, London: Printed for the author, by A[braham] J[ohn] Valpy, […], →OCLC, footnote 1, page 211:
[T]he ennead is subtracted for this cause, because the three hundred and sixty parts of the entire [circle] consist of enneads, and for this reason the four regions of the world are circumscribed by ninety perfect parts.1868, Hippolytus, J[ohn] H[enry] MacMahon, chapter XLIII, in Alexander Roberts, James Donaldson, editors, The Refutation of All Heresies, […] (Ante-Nicene Christian Library: […]; VI (Hippolytus, Bishop of Rome. Vol. I.)), Edinburgh: T. & T. Clark, […]; London: Hamilton & Co.; Dublin: John Robertson & Co., →OCLC, book IV (Of the Refutation of All Heresies), page 111:
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Rare Any grouping or system containing nine objects.
We may assert with confidence that no cycle of this kind, and of equal antiquity or even of inferior antiquity, is the actual existence better attested or more thoroughly authenticated than that of this octaëteris of Philammon of Delphi, or, as we may truly call it, this original Pythian ennead of primitive Hellas.1852, Edward Greswell, “On the Lunar in Contradistinction to the Solar Modifications of the Primitive Calendar”, in Fasti Temporis Catholici and Origines Kalendariæ. … In Four Volumes, volume I, Oxford: At the Oxford University Press, →OCLC, section V (The Octaëteris), pages 566–567:
The exquisite language of the prophecy of Isaiah, especially in its last three enneads, may have had a nearer primary reference to, and a nearer fulfilment in, the return of the exiles under Zerubbabel, and Ezra, and Nehemiah; […]1882, The Church Quarterly Review, volume XIII, London: Society for Promoting Christian Knowledge, →OCLC, page 172:
1 more example
At one time one god was a greater favourite with the nation than another, and the cult of the god or gods which the old Babylonians preferred in the early days of their empire frequently fell into disuse and neglect in after times. The most important ennead among the Babylonians was as follows:— […]1884, E[rnest] A[lfred] Wallis Budge, “The Babylonian Religion”, in Babylonian Life and History (By-paths of Bible Knowledge; V), London: Religious Tract Society, […], →OCLC, pages 127–128:
Human sciences, Philosophy, Sciences One of the six parts of the writings of the Greek-speaking philosopher Plotinus (c. 204–205 – 270), each containing nine treatises, compiled by his student Porphyry (c. 234 – c. 305).
Which Darkneſs is a fourth Property of the Moſaick Matter, and on which Plotinus inſiſts pretty copiouſly in this ſecond Ennead, and contends we can have no other notion of it, […]1662, Henry More, “An Appendix to the Defence of the Philosophick Cabbala”, in A Collection of Several Philosophical Writings of Dr Henry More, Fellow of Christ’s Colledge in Cambridge. […], 2nd edition, London: Printed by James Flesher, for William Morden […], →OCLC, chapter VIII, paragraph 3, page 137:
[W]e find side by side in the Enneads the positive and negative conceptions of the One.1941 April, F[rederick] C[harles] Copleston, “The Architecture of the Intelligible Universe in the Philosophy of Plotinus. An Analytical and Historical Study. By A. H. Armstrong. Pp. xii + 126. (Cambridge University Press, 1940. 7s. 6d.) [book review]”, in Christopher Dawson, editor, The Dublin Review, volume 208, number 417, London: Burns Oates & Washbourne, →OCLC, page 263: