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A statue of Neptune and Triton (c. 1622–1623) by Gian Lorenzo Bernini.[n 1] One of the senses of the word Neptunian is “of or pertaining to Neptune, the Roman god of fresh water and the sea(etymology 1, adjective sense 1).

Etymology 1[edit]

From Latin Neptūnius (of or pertaining to the Roman god Neptune), from Neptūnus (the Roman god Neptune) (possibly ultimately from Proto-Indo-European *nebʰ- (to become damp, cloudy)) + -ius (suffix forming adjectives from nouns); analysable as Neptune +‎ -ian. The English word is cognate with French neptunien (pertaining to the Roman god Neptune, pertaining to the sea, pertaining to Neptunism, Neptunian; proponent of Neptunism, Neptunist), German Neptunier (proponent of Neptunism, Neptunist).[1]


Neptunian (not comparable)

  1. (Roman mythology) Of or pertaining to Neptune, the Roman god of fresh water and the sea, the counterpart of the Greek god Poseidon.
  2. (by extension, rare) Of or pertaining to water or the sea.
    • 1740, John Dyer, “The Ruins of Rome. A Poem.”, in Poems. [...] Viz. I. Grongar Hill. II. The Ruins of Rome. III. The Fleece, in Four Books, London: Printed by John Hughs, for Messrs. R[obert] and J[ames] Dodsley, [], published 1759, OCLC 991281870, pages 42–43:
      Tyrian garbs, / Neptunian Albion's high teſtaceous food [i.e., oysters], / And flavour'd Chian wines with incenſe fum'd / To ſlake Patrician thirſt: for theſe, their rights / In the vile ſtreets they proſtitute to ſale; / Their ancient rights, their dignities, their laws, / Their native glorious freedom.
    • 1774 November, G. D., “The Tar’s Engagement”, in Sylvanus Urban [pseudonym; Edward Cave], editor, The Gentleman’s Magazine, and Historical Chronicle, volume XLIV, London: Printed [], for D[avid] Henry, and sold by F[rancis] Newbery, [], OCLC 192374019, page 534, column 1:
      Where the inſulting ſtreams of Chaos roar, / Where boiſt'rous waves the rugged ſhores ſurround, / And ſtorms and whirlwinds in the air abound, / There meet two rivals of Neptunian race, / Hoſtilities begin with fierce grimace: [...]
    • 1830, Horace, “Ode IX. To Mæcenas.”, in William Smart, transl., Horace Literally Translated for the Use of Students, London: Printed for Whittaker, Treacher & Co., [], OCLC 1003871256, page 105:
      Since lately the Neptunian admiral (Sextus Pompeius) when driven from the sea, fled with his burnt ships, having menaced those chains to Rome, which as a friend he had taken off from perfidious slaves.
  3. (by extension, geology) Formed by the action of water.
    neptunian dyke
    • 2008, Martin Hovland, “Ancient and Modern Analogues”, in Deep-water Coral Reefs: Unique Biodiversity Hot-spots (Springer–Praxis Books in Life Sciences Incorporating Aquatic and Marine Sciences), Dordrecht; Berlin: Springer; Chichester, West Sussex: Praxis Publishing, →ISBN, section 7.3.2 (Kess-Kess Formations, Morocco), page 170:
      A special character of these mounds [the Kess-Kess carbonate mud mounds] is the numerous Neptunian dikes. These are fracture systems, which have been filled with other sediments and minerals. It is suspected that these dikes represent spring conduits (seeps) during the formation of the mounds, and that the seeping fluids were of a hydrothermal nature [...].
  4. (by extension, geology, historical) Of, pertaining to, or supporting Neptunism (a discredited theory that rocks were formed from the crystallisation of minerals in the early Earth's oceans).
    • 1802, [John Murray], “Part III. Of the Arguments in Support of the Huttonian and Neptunian Theories, from the Positions of the Strata of the Globe.”, in A Comparative View of the Huttonian and Neptunian Systems of Geology: In Answer to the Illustrations of the Huttonian Theory of the Earth, by Professor [John] Playfair, Edinburgh: Printed for Ross and Blackwood, []; London: T. N. Longman, and G. Rees, OCLC 5894371461, page 106:
      In the Neptunian ſyſtem it is ſuppoſed that the poſitions of the ſtrata have been determined, partly by the figure of the baſe or ground on which they have been depoſited, and partly by their depoſition having been a ſpecies of cryſtallization.
    • 1848 April, B[ernhard] Studer, “On Mineral Metamorphism”, in Robert Jameson, editor, The Edinburgh New Philosophical Journal, Exhibiting a View of the Progressive Discoveries and Improvements in the Sciences and the Arts, volume XLIV, number LXXXVIII, Edinburgh: Adam & Charles Black; London: Longman, Brown, Green & Longmans, OCLC 926996861, page 372:
      In several important cases, it is difficult to determine to what degree the metamorphosis has extended, since it remains uncertain whether the form and structural relations of the mountain-mass are to be considered as remains of the neptunian sedimentary formation, or as a product of the metamorphosis itself; for the original form of the neptunian, as well as of the volcanic sedimentary rocks have often become so changed by erosion, and so much alike in both classes of rocks, that this distinctive character is wholly lost; [...]
Alternative forms[edit]
Derived terms[edit]
Related terms[edit]


Neptunian (plural Neptunians)

  1. (obsolete) A sailor.
    Synonyms: Neptunist; see also Thesaurus:sailor
    • 1620, John Taylor, The Praise of Hemp-seed: With the Voyage of Mr. Roger Bird and the Writer hereof, in a Boat of Brown-paper, from London to Quinborough in Kent. [], printed at London: For H. Gosson, [], OCLC 837721081; republished in All the Workes of Iohn Taylor the Water Poet: [], London: Printed by I[ohn] B[eale, Elizabeth Allde, Bernard Alsop, and Thomas Fawcet] for Iames Boler; [], 1630, OCLC 1049101215, page 66, column 2:
      You braue Neptunians, you ſalt water crew, / Sea-plowing Marriners; I ſpeake to you: [...]
  2. (geology, historical) A proponent of Neptunism.
    Synonym: Neptunist
    Antonyms: Plutonian, Plutonist, plutonist, volcanist, Vulcanist
    • 1807 October, “View of the Mineralogy, Agriculture, Manufactures, and Fisheries, of the Island of Arran, [] by the Rev. James Headrick. pp. 395. Price 10s. 6d. Constable and Co. Edinburgh: Murray, London, 1807. [book review]”, in The Literary Panorama. Being a Review of Books, Magazine of Varieties, and Annual Register, volume III, London: Printed by Cox, Son, and Baylis, [], [f]or C[harles] Taylor, [], published March 1808, OCLC 176276973, column 57:
      We are not ourselves, bigotted Neptunians or Vulcanians: we perceive difficulties whichever theory be adopted: and provided the earth be but stable under us, we are not anxiously jealous for the dignity of the trident-wielding power, or for the honour of the hammer-working deity.
    • 1813, John Mason Good; Olinthus Gregory; Newton Bosworth, “OBSIDIAN”, in Pantologia. A New Cyclopædia, Comprehending a Complete Series of Essays, Treatises, and Systems, Alphabetically Arranged; [], volume VIII (MID–OZO), London: Printed for G. Kearsley; [et al.], OCLC 733059775, column 1:
      Its [obsidian's] origin is warmly contested between the Neptunians and Plutonians, many of the latter denominating it a vitreous lava.
    • 1817 April, “Art. IV.—An Elementary Treatise on Mineralogy and Geology, being an Introduction to the Study of Those Sciences, [] By Parker Cleaveland, Professor of Mathematics and Natural Philosophy, and Lecturer in Chymistry and Mineralogy in Bowdoin College, &c. &c. Boston, 1816. Large 8vo. pp. 668.”, in The Analectic Magazine, volume IX, Philadelphia, Pa.: Published by Moses Thomas, OCLC 780179261, pages 312–313:
      As to the two theories, neither will suffice alone. The neptunian is utterly inadequate to explain the phenomena of basalt; nor can a vulcanist account for the appearance of an hydrophane.—We need both explanations. Those geologists who have travelled in the north of Europe, are generally neptunians; those who have made their observations in the south of the same regions, are generally vulcanists.
Alternative forms[edit]

Etymology 2[edit]

The planet Neptune photographed on 2 April 1990 by the US National Aeronautics and Space Administration’s space probe Voyager 2. The word Neptunian also means “of or pertaining to the planet” (etymology 2, adjective sense 2) as well as “an (imaginary) inhabitant of the planet” (noun sense 2).

From Neptune (eighth planet in the solar system) +‎ -ian.


Neptunian (not comparable)

  1. (astrology) Pertaining to the astrological influence of the planet Neptune.
    • 1987, Liz Greene; Howard Sasportas, “Your Inborn Images”, in The Development of the Personality: Seminars in Psychological Astrology, volume 1, Boston, Mass.: Red Wheel/Weiser, →ISBN, part 1 (The Stages of Childhood), pages 11–12:
      The Sun represents a masculine principle—assertion, expression and spirit. Neptune touching it brings in the qualities of sensitivity and creativity as well as weakness, dissolution, dissipation and elusiveness. If we take the Sun to represent the image of father, the person's experience of father (the Sun) will be coloured by Neptune. The father will receive the Neptunian projection and the child with this aspect will be sensitive to the father's Neptunian side.
  2. (astronomy) Of or pertaining to the planet Neptune.
    • 1851, Sears C[ook] Walker, “Researches Relative to the Planet Neptune”, in Smithsonian Contributions to Knowledge, volume II, Washington, D.C.: Published by the Smithsonian Institution, OCLC 608756746, section 2, page 17:
      After making a sketch of the Neptunian regions for the dates from 1790 to 1800, I soon came to the conclusion that the nights of the 8th and 10th of May, 1795, were the only ones that afforded a reasonable prospect of furnishing an observation of Neptune, and accordingly computed for the evening of the 10th of May, the limits of the Neptunian region, or in other words the locus of Neptune as a fixed star, [...]
    • 1874 January, [Alexander Winchell], “Art. V.—The Unity of the Physical World.”, in D. D. Whedon, editor, Methodist Quarterly Review, volume XXVI (4th Series; volume LVI overall), New York, N.Y.: Nelson & Phillips; Cincinnati, Oh.: Hitchcock & Walden, section II (Facts of Succession), subsection I (Primordial History of the Solar System), page 83:
      The planet Uranus, in like manner, detached, in process of time, a satellite, followed, in the progress of the cosmic ages, by seven others. A slow disturbing influence, supposed also to be recognized in the Neptunian system, has manifested itself in the Uranian, in an excessive obliquity of the plane of the Uranian satellites—an obliquity which considerably exceeds a right angle, [...]
    • 1995, Carolyn C. Porco; Philip D. Nicholson; Jeffrey N. Cuzzi; Jack J[onathan] Lissauer; Larry W. Esposito, “Neptune’s Ring System”, in Dale P. Cruikshank, with M. S. Matthews and A. M. Schumann, editors, Neptune and Triton (Space Science Series), Tucson, Ariz.: University of Arizona Press, →ISBN, page 733:
      For the Neptunian rings, we again expect that for Earth-based occultation data, so long as the mean particle size is substantially larger than the wavelength of observation (2.2μm). [...] In fact, photometric observations suggest that most Neptunian ring particles are sub-centimeter in size [...], so that we have .
    • 2017, Helen Klus, “The Planet Neptune”, in How We Came to Know the Cosmos: Space & Time, [United Kingdom]: The Star Garden, →ISBN, part III (Missions to Planets), paragraph 24.2, page 220:
      Neptune has a faint ring system and 14 known moons. The largest of these is Triton, which contains over 90% of the mass of all the Neptunian moons, and is the only Neptunian moon that's spherical.
Derived terms[edit]
Terms derived from Neptunian (astronomy)


Neptunian (plural Neptunians)

  1. (astrology) A person under the astrological influence of the planet Neptune.
    • 1983, Shakuntala Devi, “Characteristics of the Planets”, in Astrology for You, New Delhi: Orient Paperbacks, published 2007, →ISBN, page 54:
      To a Neptunian the common satisfaction of life seems too banal, and he often seeks the hidden mysteries of life. The advanced soul however realises that life is a dream, and a divine dream at that.
    • 2000, Liz Greene, “Neptune and the Artist”, in The Astrological Neptune and the Quest for Redemption, 1st paperback edition, York Beach, Me.: Samuel Weiser, Inc., →ISBN, page 324:
      Often the Neptunian cannot bring his or her fantasies to birth in form because the fantasy world remains a surrogate womb, static rather than flowing, a place of painless oblivion rather than a bridge between human and divine.
  2. (chiefly science fiction) An (imaginary) inhabitant of the planet Neptune.
    • 1894, Camille Flammarion, “The Planet Neptune and the Frontiers of the Solar Domain”, in J[ohn] Ellard Gore, transl., Popular Astronomy: A General Description of the Heavens: [...] Translated from the French with the Author’s Sanction, London: Chatto & Windus, [], OCLC 7927688, page 470:
      I need not say that from Neptune the earth is completely invisible, as well as Mercury, Venus, and Jupiter. Saturn is a little star which departs from the sun up to 18°. For the Neptunians the solar system appears to be composed of the sun, Saturn, Uranus, their own world, and the planet which doubtless gravitates beyond Neptune.
    • 1952, John Russell Fearn, chapter 12, in Quorne Returns (The Golden Amazon Saga; book 6), [Rockville, Md.]: Wildside Press, published 2013, →ISBN, page 102:
      We learn the energy quotient of a bogus Earthling, note how much it varies from that of a genuine one, and then proceed to carefully single out every Neptunian. It will take time, no doubt, but not perhaps as long as we think, as the percentage of Neptunians to Earthlings is small.
    • 2001, Justin McCory Martin, “March”, in Marvelous Month-by-month Writing Prompts: 250 Knock-their-socks-off Writing Prompts to Inspire Super Writing All Year Long!, New York, N.Y.: Scholastic Professional Books, →ISBN, page 43:
      Pretend that you are a visitor to Earth from the planet Neptune. When you return home you will want to describe Earthlings to your fellow Neptunians. [...] Good luck! Or as Neptunians say, "Urk bliff!"
    • 2001 April 12, Patricia Ann Pich, “Neptune”, in Out of this World: A Fairy Tale for Children of All Ages, [Bloomington, Ind.]: 1stBooks, →ISBN, pages 5–6:
      Since Neptune had been the chosen planet to help Earth work through its current series of crises, Neptunians were key beings at this time. Each visit to Earth was a specific mission for those who were chosen to travel there.


  1. ^ From the collection of the Victoria and Albert Museum in London, England, UK.


  1. ^ Neptunian, n. and adj.”, in OED Online Paid subscription required, Oxford, Oxfordshire: Oxford University Press, September 2003; “Neptunian, adj.”, in Lexico,; Oxford University Press, 2019–present.

Further reading[edit]