In the course of editing a medical article I came across the phrase in silico, which at first mystified me; fortunately, Wikipedia has an admirably thorough entry that not only defines it—”performed on computer or via computer simulation”—but discusses the propriety of the word-formation:

Contrary to widespread belief, in silico does not mean anything in Latin… “In silico” was briefly challenged by “in silicio”, which is correct Latin for in silicon (the Latin term for silicon, silicium, was created at the beginning of the 19th century by Berzelius). “In silico” was perceived as catchier, possibly through similarity to the word silicate. “In silico” is now almost universal; it even occurs in a journal title (In Silico Biology:

The Wikipedia article also provides a citation for the first use: “Using the data available in libraries […] two sets of experiments were performed on computers (experiments in silico) using the consistency of the data extracted.” (Danchin A, Medigue C, Gascuel O, Soldano H, Henaut A. From data banks to data bases. Res Microbiol. 1991 Sep-Oct;142(7-8):913-6.) I trust it will show up in the OED in due time. (Although generally I prefer that words be properly formed, I have to agree that in silico is preferable to the longer form, and hell, silicium isn’t classical anyway.)


  1. Jim Monroe’s book, Everyone in Silico, is set in a recognizable future with part of the population existing in simulation with the real world. (free and dead-tree versions available).

  2. Justin Neville says:

    Strikes me as very similar-sounding to the Italian phrase “in bilico”, meaning “in the balance”…

  3. “In silico” is a parallel with “in vivo” and “in vitro”, the two other places to do biology experiments. Using “silico” instead of “silicio” preserves the stress pattern.

  4. Certainly, sĭlex, silīcis (mf) has been known to Early Romans and their ancestors since—let me make a wild guess—the Paleolithics; the word is indeed in Lewis & Short with attestations to Plautus and Cato the Elder. To do an experiment in “that thing” would be “in silice”, and in the genitive plural (“of flintstones”) it is “silicium”, which, as I am guessing, is the derivation of the name “silicium” for the chemical element.
    This is not yet the end of similarity between “silicium” the silicon and “silex” the flint, and, since they are wildly incognate one to each other in English, Russian—to the rescue—has [krémn^ij], кремний for the former and [krémēnĭ], кремень, for the latter, perhaps formed as кремний

  5. kkm, I don’t think a genitive plural formation is necessary to explain it: it’s just silic- + -ium. Remember, people were regularly writing all sorts of stuff in Latin until very recently, so not everything has to be classical.
    I’m with LH on this one though: I think we can argue that “in silico” is attested and plausible enough that we can say that silicum is an alternate form of silicium. And it’s especially plausible if we interpret the -on of silicon as a greek 2nd declension neuter ending (course I don’t think it really is, but that’s beside the point).
    certain other widely attested scientific barbarities, however, I will not accept in “real” Latin 😉

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