While posting an answer to this question, I looked back at an answer I'd written on another site, which mentions the strange case of Latin diēs < PIt *diēm.

In particular:

The accusative form of [the Proto-Indo-European root behind Zeús and Juppiter], *dyēm (cf AGrk Zēn), also survived in Latin, in the form *diēm > diem. Uniquely, the dy here didn't become *dj > j; some scholars suggest that it evolved in a different Italic language/dialect, which didn't have the palatalization rules, then got borrowed back into Latin.

But, to my shame, I can't seem to figure out who these "some scholars" I cited actually are: I recently lost my web history, and with it all records of which particular articles I'd been reading.

And so I'm asking here: how did *diēm avoid the palatalization that created Jovis? I was under the impression that this palatalization happened back in Proto-Italic times, before Latin had split off; was there actually some Italic language that avoided the process entirely, from which Latin could have borrowed an unpalatalized *diēm? And if not, where could this notorious exception have come from?

  • Did you ever find those scholars again?
    – cmw
    Commented Jul 6, 2023 at 7:38

1 Answer 1


Diem seems to be due not to borrowing, but to Lindeman's Law. This is a reconstructed rule of PIE whereby monosyllabic words beginning with a stop+sonorant cluster (CR-) could optionally insert the vowel equivalent of the sonorant between C and R.

So in this case, a monosyllable *di̯ēm would have two alternative forms: *di̯ēm and *dii̯ēm, where the second is the "Lindeman variant".

Now in Latin, *di̯- became j-, but *di- stayed intact. So diem can be explained as the reflex of the Lindeman variant, while Jovis etc. come from the *di̯- forms.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.