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Regarding this paper, Frank Harrell writes:

One grammatical correction: Alvan Feinstein, the ‘father of clinical epidemiology’ at Yale, educated me about ‘trichotomy’. dichotomous = Greek dicho (two) + tomous (cut). Three = tri so the proper word would be ‘tritomous’ instead of ‘trichotomous’.

Uh oh. I can’t bring myself to use the word “tritomous” as it just sounds wrong. Trichotomous might just be one of those words that are just impossible to use correctly; see here.

P.S. The adorable cat above faces many more than three options.


  1. Stuart Buck says:

    By the same token, some people say they’re addicted to chocolate: “chocoholic.”

    But if it’s alcohol > alcoholic, it should be chocolate > chocolatic.

  2. Keith O'Rourke says:

    I definitely enjoyed Alvan Feinstein’s visits to Toronto in 1990s with his aggressive critical comments and humor.

    Also agreed with his encouragement to young clinical researchers to think things through for themselves rather than just asking a statistician. Unfortunately that lead many to just ignore what any statistician would ever suggest.

    Very troubling to find out about his apparent role in the _agnotological_ efforts of the Tobacco industry –

    Seems like he was encouraging excellent views of science solely? for the purpose of making good enough science impotent.

  3. Paul Alper says:

    Most of the rest of the world, including Andrew, insists the word “data” requires a plural verb. In actuality, there is an ellipsis:

    “the omission from speech or writing of a word or words that are superfluous or able to be understood from contextual clues.
    a set of dots indicating an ellipsis.”

    Consequently, when we write

    “The data”

    we mean either

    “The data set”


    “The set of data”

    In the first instance, “data” is an adjective, while in the second instance, “data” is the object of a preposition. Some of the confusion is that in the U.S., the collective noun, “set” takes a singular verb while in the U.K. the tendency is for a collective noun to require a plural verb. For example, in the U.S., “Congress is in session” while in the U.K. “Parliament are meeting.”
    As to the word, “datum,” it appears to exist only in the field of geodesy, and its plural is (quite Anglo-Saxon logically) “datums”

    “A geodetic datum (plural datums, not data) is a reference from which spatial measurements are made. … ” Note the ellipsis!

  4. ghenly says:

    David J. Weiss addressed a similar issue, polychotomous vs. polytomous in an editor’s note in Applied Psychological Measurement in the 1990s and decided in favor of polytomous.

  5. In “The Word’s Gotten Out” (1989), Willard R. Espy suggests playfully that “trichotomy” could mean “haircut” (“tricho-,” “hair,” and “tomia,” “cutting”). While skeptical–as far as I know, the Greek “tomia” is not used with hair–I enjoy the idea.

  6. Phil says:

    Way back in 2006, “derrida derider” pointed out that if a prisoner escapes from a prison, the prisoner is an escaper, not an escapee. derider claims the guards are the escapees, but that’s wrong, the prison itself is the escapee. This puts me in mind of David Owen, in his essay about a meeting of meeting planners, pointing out that the people who attend a meeting are the attenders; the meeting itself is the attendee.

  7. Emmanuel Charpentier says:

    Ahem… I’m sorry to be commeled to split hairs :

    “Tricho” irresistibly evokes “τριχοσ”, (irregular) genitive of “θριχ”, which means “hair”, according to [](Bailly) . “Trichotomy” would then evoke the act of splitting hair(s).

    Which is not, of course, without some linkage to the subject of the paper, but not in the (probably) intended sense…

    On the other hand, Frank Harrel is right : the act of cutting something in three parts may, indeed, be rendered as “tritomy”, but, unless a Greek derivation is needed (ex : medical vocabulary pedantry), I’d rather use “trisection”.

    Hoping (but not really expecting) this helps…

  8. Merriam-Webster disagrees:

    >Origin and Etymology of trichotomous
    >Late Greek trichotomein to trisect, from Greek tricha in three (akin to treis three) + -tomein (akin to temnein to cut)

    There is no “tritomy” nor “tritomous” in that dictionary, and a Google search for their definitions returns no relevant results.

    M-W *does* contain “polytomy” and “polytomous,” however.

    • Emmanuel Charpentier says:

      Bailly (same reference as before) gives two entries for “τριχα” :

      * “In three parts” : this goes with Merriam-Webster… ;

      * singular accusative of “θριχ” : this goes with “hair splitting”.

      The context is therefore necessary to disambiguate possible uses of “trichotomy”. Being lazy, I’d rather use “trisection” for the first meaning and “trichotomy) for the second.

      Which, BTW, seems rather more prevalent nowadays (MW states that the first known use of “trichotomous” was in 1800)…

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