Was the 'i' in cuius pronounced as 'j' or did it form a diphthong with 'u'

Question

You can't determine from metrical feet if the 'i' in 'cuius' was pronounced as 'j' or if it formed a diphthong with 'u'. Diphthongs always form long syllables so it could be the 'u' was long and the 'i' was pronounced as 'j' or it could be that 'ui' formed a diphthong. Do we have any other way of knowing this information? Further, most modern dictionaries assert that it should be pronounced as 'cujus', well, why do they believe this?

Also, there are the few times when Latin got transliterated into Greek. Does anyone know if 'cuius' or other such words were ever inscribed in stone in Greek?

Answer 1

The i in cuius was pronounced as /j/. We can arrive at this conclusion several ways:

Firstly is the history of spelling variations: the standard spelling of cuius was not always cuius, and was previously quoius until the early empire. The quo became cu (like cum from earlier quom), meaning u stood in for a vowel. Other spellings I think are also attested, such as cuiius, where the double ii is very probably an attempt to represent a geminate /jj/. That being said, I do not know when or by who these spellings occured.

As for the usual orthography of Latin that we're used to, cu is used when u is a vowel, and qu when u is a consonant. That's why Romans could distinguish between qui (/kʷiː/) and cui (/kui̯/).

Etymology is another note: cuius comes either from Proto-Indo-European *kʷosyo (gen. sg. of the relative pronoun) or *kʷo-s-yo-s (an adjective derived from the same pronoun). Either way, the /s/ assimilated to the /j/, giving us a geminate /jj/, which explains the spellings that reflect that.

Answer 2

Cuius is typically thought to have been pronounced as /kuj.jus/ with short /u/ (which was possibly realized phonetically as [ʊ]) followed by geminate (i.e. long, or doubled) /j.j/.

The phonetic difference between [j] and non-syllabic [i] is practically negligible, and the phonological difference between /j/ and non-syllabic /i/ is often questionable as well. There are analyses of modern English that treat words like “eye” and “toy” as ending in /j/, although the usual analysis is that these words contain diphthongs.

As NanoEta mentions, cuius comes from quoius; however, I think quoius had a short o, not a long one.

As I say in my answer to the question "What is the etymology of 'cuius' and is it different from 'quis'?", I've read a 1902 paper by Charles Exon which supposes that huius and cuius developed long /uː/ from coalescence of an oi diphthong followed by j (he describes the development as "hoi-jus" to "hū-jus"); however, I know of no modern source that takes this view.