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.


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

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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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)

  • 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


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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