from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun Biology A group of closely related organisms that are very similar to each other and are usually capable of interbreeding and producing fertile offspring. The species is the fundamental category of taxonomic classification, ranking below a genus or subgenus. Species names are represented in binomial nomenclature by an uncapitalized Latin adjective or noun following a capitalized genus name, as in Ananas comosus, the pineapple, and Equus caballus, the horse.
  • noun Logic A class of individuals or objects grouped by virtue of their common attributes and assigned a common name; a division subordinate to a genus.
  • noun Chemistry A set of atoms, molecules, ions, or other chemical entities that possess the same distinct characteristics with respect to a chemical process or measurement.
  • noun A kind, variety, or type.
  • noun The outward appearance or form of the Eucharistic elements that is retained after their consecration.
  • noun Either of the consecrated elements of the Eucharist.

from The Century Dictionary.

  • noun An appearance or representation to the senses or the perceptive faculties; an image presented to the eye or the mind.
  • noun Something to be seen or looked at; a spectacle or exhibition; a show.
  • noun In logic, and hence in ordinary language, a class included under a higher class, or, at least, not considered as including lower classes; a kind; a sort; a number of individuals having common characters peculiar to them.
  • noun One of the kinds of things constituting a combined aggregate or a compound; a distinct constituent part or element; an instrumental means: as, the species of a compound medicine.
  • noun In biology, that which is specialized or differentiated recognizably from anything else of the same genus, family, or order; an individual which differs, or collectively those individuals which differ, specifically from all the other members of the genus, etc., and which do not differ from one another in size. shape, color, and so on, beyond the limits of (actual or assumed) individual variability, as those animals and plants which stand in the direct relation of parent and offspring, and perpetuate certain inherited characters intact or with that little modification which is due to conditions of environment.
  • noun Coin; metallic money; specie. See specie.
  • noun One of a class of pharmaceutical preparations consisting of a mixture of dried herbs of analogous medicinal properties, used for making decoctions, infusions, etc. See under tea.
  • noun In civil law, the form or shape given to materials; fashion; form; figure.
  • noun In mathematics: A letter in algebra denoting a quantity.
  • noun A fundamental operation of arithmetic. See the four species, below.
  • noun A former standard of currency in certain parts of Germany and in the north of Europe, apparently answering to the modern dollar of commerce.

from the GNU version of the Collaborative International Dictionary of English.

  • noun rare Visible or sensible presentation; appearance; a sensible percept received by the imagination; an image.
  • noun (Logic) A group of individuals agreeing in common attributes, and designated by a common name; a conception subordinated to another conception, called a genus, or generic conception, from which it differs in containing or comprehending more attributes, and extending to fewer individuals. Thus, man is a species, under animal as a genus; and man, in its turn, may be regarded as a genus with respect to European, American, or the like, as species.
  • noun In science, a more or less permanent group of existing things or beings, associated according to attributes, or properties determined by scientific observation.
  • noun A sort; a kind; a variety
  • noun obsolete Coin, or coined silver, gold, or other metal, used as a circulating medium; specie.
  • noun obsolete A public spectacle or exhibition.
  • noun A component part of a compound medicine; a simple.
  • noun (Med.) An officinal mixture or compound powder of any kind; esp., one used for making an aromatic tea or tisane; a tea mixture.
  • noun (Civil Law) The form or shape given to materials; fashion or shape; form; figure.
  • noun (Zoöl.) a subspecies, or variety, which is in process of becoming permanent, and thus changing to a true species, usually by isolation in localities from which other varieties are excluded.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun A type or kind of thing.
  • noun A group of plants or animals having similar appearance.
  • noun biology, taxonomy A rank in the classification of organisms, below genus and above subspecies; a taxon at that rank
  • noun mineralogy A mineral with a unique chemical formula whose crystals belong to a unique crystallographic system.
  • noun obsolete The image of something cast on a surface, or reflected from a surface, or refracted through a lens or telescope; a reflection.
  • noun Roman Catholicism Either of the two elements of the Eucharist after they have been consecrated, so named because they retain the image of the bread and wine before their transubstantiation into the body and blood of Christ.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun (biology) taxonomic group whose members can interbreed
  • noun a specific kind of something


from The American Heritage® Dictionary of the English Language, 4th Edition

[Middle English, logical classification, from Latin speciēs, a seeing, kind, form; see spek- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin speciēs ("appearance; quality"), from speciō ("see") + -iēs suffix signifying abstract noun.


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  • Action and reaction does not produce the species, nor yet _another species_.

    The Christian Foundation, Or, Scientific and Religious Journal, February, 1880 Various

  • This consideration leads us to treat of the main objection raised to every descent theory: namely, that never yet has the origin of one species from another been observed, but that, on the contrary, _all species_ -- so far as our experience goes, stretching over thousands of years -- _remain constant_.

    The Theories of Darwin and Their Relation to Philosophy, Religion, and Morality Rudolf Schmid

  • He might reply to the dilemma by saying, species do not exist _as species_ in the sense in which they are said to vary (variation applying only to the concrete embodiments of {272} the specific idea), and the evolution of species is demonstrated not by individuals _as individuals_, but as embodiments of different specific ideas.

    On the Genesis of Species St. George Mivart

  • A change of conditions occurs which threatens the existence of the species, but the _two varieties_ are adapted to the changing conditions, and, if accumulated, will form two new _species adapted to the new conditions_.

    Alfred Russel Wallace: Letters and Reminiscences, Vol. 1 James Marchant

  • The fact is, we do not know of the origin of any two species of animals that do not cross and whose offspring are not fertile; in other words, we do not know of the origin of _species, _ but only of _varieties_.

    Evolution An Investigation and a Critique Theodore Graebner 1913

  • Just in so far as they have adjusted themselves to live in and overcome the opposition of the body-tissues of a certain species of animals, _just to that degree they have incapacitated themselves to live in the tissues of any other species_.

    Preventable Diseases Woods Hutchinson 1896

  • It has now been shown, though most briefly and imperfectly, how the law that "_Every species has come into existence coincident both in time and space with a pre-existing closely allied species_," connects together and renders intelligible a vast number of independent and hitherto unexplained facts.

    Contributions to the Theory of Natural Selection A Series of Essays Alfred Russel Wallace 1868

  • The immutability of species, _as he defined species_, was the logical consequence of this theory, and that, it seems to me, is the substantial difference between him and Darwin.

    The Autobiography of a Journalist, Volume I William James Stillman 1864

  • These properties, then, which were connoted by the name, logicians seized upon, and called them the essence of the species; and not stopping there, they affirmed them, in the case of the _infima species_, to be the essence of the individual too; for it was their maxim, that the species contained the

    A System Of Logic, Ratiocinative And Inductive (Vol. 1 of 2) John Stuart Mill 1839

  • These properties, then, which were connoted by the name, logicians seized upon, and called them the essence of the species; and not stopping there, they affirmed them, in the case of the _infima species_, to be the essence of the individual too; for it was their maxim, that the species contained the

    A System Of Logic, Ratiocinative And Inductive John Stuart Mill 1839

  • The strange sorrow we feel when we confront this world without our fellow creatures has a name: “species loneliness.”

    The secret movement bringing Europe’s wildlife back from the brink Isobel Cockerell 2023


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  • When spechifying spechific, spechious spechimens, it can be espechially helpful to regard the lack of 'h' in the word 'species'. Unless, of course, you do your research in Yiddish. :)

    December 8, 2006

  • actually, the OED specifies only two variants: /'spi�?ʃi�?z/ and /'spi�?ʃɪi�?z/ — that is, not a "speesees" in sight!

    November 27, 2007

  • Spell-checking tools tell me the following is incorrect:

    "the species's ecology"

    and suggest "the species' ecology" instead.

    I believe this means switching to the plural, doesn't it?

    March 29, 2011

  • I think the spell-checker is being overly prescriptive, and it's really a matter of taste.

    Personally I would use the s here: "the species's ecology".

    Of course you could always rephrase: "the ecology of the species..."

    March 29, 2011

  • Whether you add " 's" or just an apostrophe depends on the pronunciation, not whether the word is singular or plural. "Douglas's watch" is correct because it's pronounced "Douglases". "Specieses" sounds wrong, so I'd use "species' ecology" rather than "species's ecology".

    March 30, 2011

  • But it doesn't sound wrong to me.

    The meaning should be clear from the context, but if not, then "species's" - at least to my ear - is clearly singular, whereas "species'" could refer to the ecology of one, or more than one, species.

    March 30, 2011

  • Please note that the sentence does indeed refer to a single species.

    March 30, 2011

  • I was under the impression that you can only use the s' construction on possessive plurals, and indeed, that the whole point of s' is to indicate a possessive plural. For example, consider "The cat's eyes glinted in the dark" and "The cats' eyes glinted in the dark". The placement of the apostrophe tells you how many cats there are.

    I could easily be wrong, though. Anyone care to find an authoritative source?

    March 30, 2011

  • "The lens's focal length is 50 millimeters." What do you guys think of this construction? "Lens" is another singular word that ends in S, but unlike "species", its has a plural that's different from the singular.

    March 30, 2011

  • Well, with lens, it's easy: "lens's" indicates singular, "lenses'" plural. The problem with species is that unlike lens, it's plurale tantum.

    I favour "species's" when the genitive singular is intended. Because that apostrophe-ess is a marker of gen. s., whereas the ess-apostrophe denotes gen. plural. But maybe it's not so obvious to other people?!

    March 30, 2011

  • It's not plurale tantum, as it readily occurs as both singular and plural in syntax; however, the two forms are the same, like sheep and aircraft.

    This problem hadn't occurred to me before, but I agree in theory that singular species's is possible. However, we use apostrophe-only with certain singular words, such as classical names ending in multiple sibilants: Xerxes', Rameses', Jesus'. It's the difficulty of pronouncing the extra syllable that recommends the apostrophe-only, as it would in the narcissus' petals.

    March 30, 2011

  • More on Saxon genitive.

    March 30, 2011

  • According to The Gregg Reference Manual, "if the addition of an extra syllable would make a word ending in an s hard to pronounce, add the apostrophe only." It includes "Moses' flight from Egypt" and "Euripedes' plays" as examples of this kind of possessive with a singular noun.

    The sentimental favorites Strunk and White recommend 's "whatever the final consonant," but they allow exceptions for ancient names and "such forms as for conscience' sake." Even then, they point out that "Moses' Laws" can be replaced with "the laws of Moses." (That trick for recasting the sentence is why I was looking up the Saxon genitive.)

    I usually vote for recasting the sentence if what you're working on sounds awkward (or causes you to have to get out more than one style guide).

    March 30, 2011

  • Just be thankful that the species the ecology of which you're talking about isn't itself the property of Moses.

    March 30, 2011

  • Or the property of Len.

    March 30, 2011

  • Or lent by Len to Moses.

    After all this discussion, I still favour the s.

    March 30, 2011

  • Trying to figure out why "species's" sounds wrong to me, I come up with two possibilities. As a practicing biologist, I don't hear other biologists saying it, although biologists often do write "species's". Also, "species" sounds plural even though it can be singular, echoing "crises" and "bases". Difficulty of pronunciation doesn't seem to be a factor: "Moses's" and "Jesus's" don't sound wrong to me. I think the answer is that "species's" is generally pronounced the same way as "species", so the distinction is made in writing, not in speech.

    March 30, 2011

  • Is there a specific style manual used by biologists?

    March 30, 2011

  • Yes, the CBE Manual (1994). I have a copy in my office at work, so I'll see what it has to say about possessive species. (CBE stands for Council of Biology Editors; it's been supplanted by the Council of Science Editors.)

    March 31, 2011

  • Chucky D had a sage editor with 'Origin of Species'.

    March 31, 2011

  • Cf. specie and specious.

    March 31, 2011

  • The CBE manual doesn't specifically address the possessive of "species". It does have a few of relevant guidelines: "The general principle of adding an apostrophe and "s" holds for most nouns, including proper nouns, that end in "s". Pronunciation can serve as a guide: if one would pronounce the possessive "s", it should appear in the written form". "If in a particular case the double sibilant sounds awkward, the sentence should be recast to avoid the possessive form altogether." "The possessive forms of Greek and hellenized names of more than 1 syllable ending in "s" (which often have an unaccented ending pronounced "eez", as well as those of "Jesus" and "Moses", are formed by adding an apostrophe only."

    March 31, 2011

  • singular!

    January 27, 2012