Most modern editions don't distinguish vocalic I from consonantal J. Most of the time, this doesn't create any real ambiguity.

However, for certain purposes it can be useful to know the difference: for example, when reading a passage out loud, or for composing metered poetry.

If I have a text that marks everything except I vs J, what's the best way to automatically determine the difference? My goal is a program that can go through and mark Js without human intervention—so it doesn't matter how complicated that system is, so long as it doesn't require specific human knowledge (so Asteroides's otherwise-excellent suggestion to look at English derivatives doesn't help me).

For a definite example: how can I know that Jūlius and Troja have a J, but Iūlus and Gāius have an I? Is there a reliable dictionary that lists this, for example, even in the case of proper names? Or is the best option to implement Alex B's general rules and not worry about the occasional error in a Greek loan?

(Bonus points if this can also recognize "hidden" Js before /i/, as in ejiciō.)

  • Related: latin.stackexchange.com/q/14/406
    – Draconis
    Aug 4, 2020 at 17:33
  • I've always thought Troia was trisyllabic -- is this not the case?
    – TKR
    Aug 4, 2020 at 19:00
  • Perhaps you should note that this is a subset of the question you asked yesterday latin.stackexchange.com/questions/14291/…
    – C Monsour
    Aug 4, 2020 at 19:12
  • @CMonsour Related, but here I'm wondering if there's a way to distinguish them easily, there I'm wondering what distinctions exist. (I can delete this one if it's too similar though.)
    – Draconis
    Aug 4, 2020 at 19:36
  • 1
    @Draconis I don't think you should delete this. But a cross-reference would be nice. (from that one to this one).
    – C Monsour
    Aug 4, 2020 at 20:55

1 Answer 1


This already exists. At http://alatius.com/macronizer you can tick the option "convert i into j" (as well as "u into v"). It works most of the time, but I don't know how. It probably checks a list of exceptions before it applies some general rules.

  • 1
    It might be worth adding that the source is available, as well.
    – Draconis
    Aug 13, 2020 at 15:02
  • @Draconis It looks like it just has a major master list!
    – cmw
    May 11, 2021 at 17:53

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