"Eundem" is the correct accusative of "idem". However, I saw "eumdem" in various texts of medieval and/or Church Latin. So I wonder:

  • when did "eumdem" start to be used, perhaps by non-native Latin users?
  • when did it become a regularly accepted alternative to "eundem" (this might not be distinguishable from previous subquestion though)?
  • did "eumdem" ever completely replace "eundem" in some time and region (not counting times/regions with very few written records)?
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    This is an example of phonological dissimilation (en.wikipedia.org/wiki/Dissimilation)—in this case, the dental consonant [n] dissimilating from the dental consonant [d] to become the labial consonant [m]. But I don't know the answer to your question, and I can't even think of an example in English, so I'm leaving this as a comment rather than an answer. :) Commented Feb 23, 2016 at 19:55
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    Another keyword is sandhi. A classical example being words like symbiont (syn-biont).
    – Wrzlprmft
    Commented Feb 23, 2016 at 20:18
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    @Joel Derfner: I’d rather say eundem is an example of assimilation, because the “expected” form would indeed be eumdem (compare eum). There was lots of variation in whether this assimilation appeared in writing or not, especially visible with the prefix in- (im-, ir-, il-, i-)
    – chirlu
    Commented Feb 23, 2016 at 20:50
  • @chirlu Hmm. I'm not sure I agree. If it were "eunbem," then "eumbem" would be the expected form. but [d] and [n] are both dentals, whereas [m] is labial. Commented Feb 23, 2016 at 22:23
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    @Joel Derfner: Are you aware that the first part of eundem is eum, with the -m being the accusative ending?
    – chirlu
    Commented Feb 23, 2016 at 22:26

1 Answer 1


Using the texts stored in the Latin Library as a guide, we can see that the prevalence of eumdem waxes and wanes through history. Its earliest significant use in writing appears to be approximately the 4th century, and it reaches its height in the late Medieval period, but even then it does not displace eundem.

Earliest usage

Several works from the post-classical era employ eumdem rather than eundem; here are some examples:

Of course, this analysis assumes that the transcriptions available on Latin Library have not been altered from the originals. They seem to indicate, however, that eumdem was at least occasionally employed in this time period. Still, many other authors of this time preferred eundem: Augustine himself used that form in several other works, and examples of this usage abound in Ammianus, Justinian, and Bede.

Late Medieval usage

Several prominent authors in the 12th century make extensive use of eumdem, perhaps marking a high point of its usage. They include:

Even in this time period, however, other authors continued to use eundem. The Latin Library includes Aquinas, Gregory VII, Gregory IX, and the Magna Carta in this category, though a more thorough investigation of Aquinas's works reveals a fairly even split between the two forms.


Following the Medieval period, most authors seem to adopt the use of eundem. Among them are Spinoza and Descartes, though Erasmus is a notable exception; his Institutes, for example, include eumdem several times.


I don't see any clear patterns of the use of eumdem, whether by time or by geography. Examples of it exist back to at least Late Latin, and it was more widely employed in the late Medieval period. But it does not appear to have ever achieved dominance over eundem.

  • Nice, +1. I'll wait a day or two before accepting it. Btw. I remember seeing "eumdem" somewhere in Aquinas, but I don't remember where - but it might have been a "correction" by some later scribe, or even in his homilies, that were only translated to Latin.
    – Pavel V.
    Commented Mar 5, 2016 at 19:06
  • @PavelV. Here's the Google search of Latin library for Aquinas: it finds nothing for eumdem and 8 results for eundem. So yes, perhaps a transcription error or scribal modification took place. Unfortunately a really definitive answer would require a corpus of carefully transcribed Medieval manuscripts, and if one of those exists I'm not aware of it. Commented Mar 5, 2016 at 19:15
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    For the most comprehensive online collection of Aquinas' works, dhspriory.org/thomas, I found 65 times "eumdem" and 94 times "eundem". The Latin Library is good, perhaps the best single site for discerning long-time trends, but they don't have everything.
    – Pavel V.
    Commented Mar 5, 2016 at 19:31
  • for future reference the dhspriory.org content has been taken down but I believe corpusthomisticum.org is entirely comprehensive in any case.
    – Ben Dunlap
    Commented May 13, 2020 at 11:55

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