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

  • noun Division into three parts or elements.
  • noun A system based on three parts or elements, especially the theological description of humans as consisting of body, soul, and spirit.

from The Century Dictionary.

  • noun Division into three parts; specifically, in theot., division of human nature into body (soma), soul (psyche), and spirit (pneuma).

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

  • noun Division into three parts.

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

  • noun Division or separation into three groups or pieces.
  • noun algebra the following property of an order relation (e.g., "less than"): for any two elements (of a given algebraic structure) there are exactly three possibilities: either the first element is less than the second one, the second element is less than the first one, or the two elements are equal.

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

  • noun being threefold; a classification into three parts or subclasses


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

[New Latin trichotomia : Greek trikha, in three parts; see trei- in Indo-European roots + New Latin -tomia, -tomy.]


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  • In phylogenetics, a trichotomy is an unclear or unknown evolutionary relation among three species. The etymology is (erroneously, as far as I know)* copied from dichotomy (see cranberry morpheme).

    What they forgot is that the word trichotomy already existed, but it means... haircut (θ�?ίξ + τομή).

    (* I was wrong! follow discussion for further details)

    May 4, 2008

  • Pro: Why do you reference 'cranberry morpheme' here? Which part of 'trichotomy' are you suggesting is one?

    You are making a subtle joke, yes?

    May 4, 2008

  • If you remove "berry" from a "cranberry", you get a meaningless cran. What happened here, apparently, is that someone took the word dichotomy (whose etymology is δίχα, "asunder", + τομή) and removed the "di" (δ�?ο, in ancient Greek, meaning "two") part, and what's left is a meaningless "chotomy".

    The reference to "cranberry morpheme" was intended to help understanding this (even if I guess the phenomenon is similar, but not the same).

    May 5, 2008

  • I'm obviously missing something. polychotomous/polychotomy are legitimate words. So, according to you, are dichotomous/dichotomy. yet, somehow, trichotomous/trichotomy are not? Why not? Both the di- and tri- prefixes just seem like specific instances of the poly- case.

    May 5, 2008

  • If your argument is somehow that 'dicho'-tomous and 'polycho-tomous' are OK, but 'tricho'-tomous is not, because 'tricho' is a root related to 'hair' (no pun intended), then I think it's not a very strong argument. This kind of non-uniqueness of roots happens all the time - for instance, the morpheme 'sex' sometimes relates to the number six, sometimes has to do with 'sex', but neither excludes validity of the other. Again, I may not be understanding your argument correctly. But I don't think the cranberry morpheme analogy is valid, or helpful.

    May 5, 2008

  • Help me understand. Are they really legitimate words? In which sense? I never found an etymology that does not redirect to "dichotomy", supporting the analogy rather than the etymology hypothesis. In fact, the word more commonly used is polytomy.

    May 5, 2008

  • If you google search τ�?ίχα (hypothetically, "in three parts", in analogy with δίχα) you can't find that meaning (apparently, it means hair in modern Greek - but I'm not sure).

    May 5, 2008

  • I've heard of spliting tricho's but this is ridiculous...!

    May 5, 2008

  • I don't understand your point, quite frankly. trichotomy and polychotomy are perfectly legitimate words. You appear not to like that, for hairsplitting reasons of your own, but there's no argument about their legitimacy.

    And the idea that any English speaker is going to confuse trichotomy with getting a haircut is quite silly, to be honest.

    May 5, 2008

  • ?

    What are we talking about?

    Please read my first and second comments, and you will see that what I mean is expressed there. A corrupted etymology.

    May 5, 2008

  • Update: I found a dictionary ("The free dictionary") that gives the τ�?ίχα etymology - unfortunately, with no external reference. I will let you know if I find out more.

    May 5, 2008

  • I don't know ancient Greek, or if tricho- is a "legitmate" – i.e. etymologically justified – morpheme, but what Prolagus is talking about is the way we form words by analogy when we think we understand what the parts mean. Hence words like "prequel" by analogy with "sequel," although the -qu- is an instrinsic part of the root sequ-, meaning "follow" (as in sequence, subsequent, etc.) and prequ- as a morpheme is nonsense.

    On a lighter note, the dichotomy–trichotomy strings (are tetrachotomy, pentachotomy, hexachotomy, etc. possible?) reminds me of the common but not-very-clever attempt at word play you hear when someone says, "I'm in!" followed by "Me, too!" then "Me three!"

    May 5, 2008

  • A phone call to Italy helped me find what I was looking for.

    1) τ�?ίχα exist, and means "in three parts". So my first comment should be corrected in (erroneously, as far as I know) (correctly).

    2) Neither πολίχα nor πολ�?χα can be found (at least in the best Greek to Italian translation dictionary). So all the previous discussion can be all referred only to polychotomy (until anyone has proof to the contrary).

    Having said that:

    I will probably take a break.

    See my profile for further details.

    (Thank you, rolig! You really got what I meant!)

    May 5, 2008

  • Pro: Sorry, you're right - you make your point quite clearly in your earlier posts. I think all it really boils down to is a difference of opinion, or maybe a difference in philosophy. Specifically, I don't find the term 'corrupted etymology' (and the implicit judgement therein) particularly helpful when applied to a particular evolution of the language which has already happened. It has a certain academic interest, but in this particular instance, it seems that 'trichotomy' and 'polychotomy' are well-established, so that there's no turning back the clock.

    I think these kind of etymological 'wrong turns' are more of a cause for celebration than regret - they are a kind of testament to the fundamental unpredictability of the evolution of language. rolig's prequel-sequel example is another good illustration of the phenomenon, which I suspect is fairly widespread.

    What, in your opinion, is the correct singular form of the plural noun syringes? :-)

    Upon re-reading my previous posts in this thread, the tone is a little terser than I intended - sorry about this. But you know I just enjoy a good discussion..

    May 5, 2008

  • That's OK - all explained, no miscomprehensions left. I'm serious about that, I really accept your apologies!

    But still, I want to think a bit about Wordie, for a while.

    May 5, 2008

  • In evolutionary biology trichotomy and polychotomy are not used to mean "three cuts" or "multiple cuts". I'll agree that the original meaning of trichotomy corresponds to its etymology, but it's not clear this is true of polychotomy, which might well provide an example of a cranberry morpheme. "Chotomy" seems to be taken to mean "branching" rather than "cutting".

    In an evolutionary analysis, a dichotomy represents a place where a lineage split into two (a speciation event). But a trichotomy or a polychotomy represents a failure to identify the splits of lineages. It would be extremely rare for a trichotomy or polychotomy to mean that there actually was a simultaneous three-way or multi-way split. There is no cutting or splitting, just an apparent trifurcation or multifurcation that is recognized as an artifact of the analysis.

    See tetrapyloctomy.

    May 5, 2008

  • trichotomy of power

    January 23, 2012