(This answer is based on Weiss's Historical and Comparative Grammar of Latin and Clackson and Horrocks's Blackwell History of the Latin Language.)
The first thing to know about these two ablative endings, -e and -ī, is that neither of them is descended from the Proto-Indo-European (PIE) ablative ending.
-e comes most probably from the PIE locative ending, *...
Short answer: Latin does not allow the sequence ts (except in compound words), so an expected form like monts was remade into mons.
Of course, this only leads to the further question of why this sequence was disallowed in Latin, which is much more difficult to answer. Every language has a set of preferences as to which sequences of sounds it does and doesn'...
The usual explanation given in historical grammars, e.g. those of Weiss, Sihler, and Buck, is that the -er- stems result from regular sound change, while the -or- stems result from analogical remodeling on the basis of the nominative/accusative.
A well-known Latin sound change turned all short vowels in word-medial open syllables to i. Since short ...
I have run a quick analysis using data from latinlexicon.org. I included adverbs ending in -ter (about 820). Most end in -iter (the rule). A good number end in -nter (which as you know are formed with syncopation regularly when the base adjective/participle ends in -nt). The remainders are a mix of declinables and indeclinables (e.g., propter is indeclinable ...
As a first note, I think it would be helpful to understand the morphology of these third-declension neuter nouns in -ma as they appear in Greek:
Nominative ὄνομᾰ ὀνόμᾰτᾰ
Genitive ὀνόμᾰτος ὀνομάτων
Dative ὀνόμᾰτῐ ὀνομάσῐ(ν)
Look at older forms.
(See the end of this post for a tl;dr.)
For example, consider the third-declension noun lār, laris ("home spirit"). In Classical Latin this seems to be a standard R-stem noun: lār, laris, larī, larem, lare...
But in some very archaic Latin (such as the Carmen Arvale), the nominative plural is given as lases. This could mean that it ...
A synchronic analysis: deletion of coronals before s within a syllable
In "Latin Rhotacism for Real," Kyle Gorman describes the deletion of /t/ in the nominative form of words like mons, montis as part of a larger pattern of deletion of coronal consonants which also applies to words like pes, pedis and pollis, pollinis. The main argument of the paper is ...
For what it's worth, I think this was simply a mistake.
Greek nouns ending in -is are generally third-declension i-stems, like póli-s. In Attic, these nouns tend to show an -i- in some forms and an -ei- in others, with no particular logic that I've ever learned; quantitative metathesis and contraction then make the forms even less predictable. The genitive ...
The loss of the final consonant of –t stems before the –s suffix of the nominative singular is not specific to Latin, but is general Indo-European. It is thus not correct to try to explain it in terms of some inner-Latin exclusion law. It is something that Latin has inherited from IE.
Example: IE *nepōt-, nom. sing. *nepōt-s > *nepōs > Iranian *napāh > ...
The general rule is that in Latin etymological s becomes r between two vowels. Thus nom. honos, but gen. honoris (but also nom. honor by analogy to the other cases). Words like honestus confirm that this is indeed an s-stem.
The definition of "I-stems" is relevant
Although the question said to ignore i-stems, I think it's actually necessary to discuss them, because many Latin nouns of the third declension have a mix of i-stem and consonant-stem forms (to the extent that the division of nouns into these two categories is fairly problematic). And i-stem nouns, as the name implies,...
Here are some examples of different stem-final consonants:
B: plēbs, plēb-
C: dux, duc-
D: lapis, lapid-
G: rēx, rēg-
H: Iphis, Iph-
L: sōl, sōl-
M: hiems, hiem-
N: nōmen, nōmin-
P: apis, ap-
R: ōs, ōr-
S: os, oss-
T: mīles, mīlit-
V: Iuppiter, Iov-
X: axis, ax-
I found nothing with F.
I am not aware of any third declension nouns whose stem ends in a ...
The usual form used in Classical Latin seems to have been plura. I don't know of any "good reason" to choose plura aside from that.
The discrepancy between plura and plurium was noted by past authors. The main historical source I've seen mentioned1 that discusses pluria is Aulus Gellius, who in Noctes Atticae 5.21 recounts an anecdote where a friend of his ...
It's not just vatēs - see Weiss pp 243-244 for details. He mentions 30 i-stem hysterokinetic nouns that have -ēs ending in nom.sg. (instead of the expected -is), for example: aedēs, caedēs, cautēs , cladēs etc.
I am aware of two proposals.
Analogical leveling in Latin
Some researchers have claimed that nom.sg. -ēs is due to analogical leveling after acc....
Here are all the references that I have found so far that have relevant information about the declension of nouns ending in -es that come from Greek. These references don't specifically mention Arsaces and Gotarzes.
Allen and Greenough:
Many Greek nouns vary among the 1st, the 2nd, and the 3rd declensions.
Boōtae (genitive of Boōtēs, -is),
The clearest examples of third-declension adjectives that have attested consonant-stem forms in the neuter nominative/accusative plural seem to be the following:
the class of comparative-declined adjectives, such as neuter plural nominative/accusative adjectives ending in -iōra (including maiōra/majōra) and minōra
vetera. It is thought that vetus was ...
I don't know enough to give a detailed answer, so this is just some basic information to start with.
Speaking generally, -īs is an "i-stem" accusative plural ending, so it's expected to go along with -ium in the genitive plural, -ī in the ablative singular, and -ia in the neuter nominative/accusative plural.
But the actual use of "i-stem" forms wasn't ...
It looks as though there are three stages:
First: inherited adverbs ending in -ter, like praeter, subter, propter (IE -ter-).
Second: the ending -ter is abstracted from these and attached to the stem of an adjective, as in brevi-ter, gravi-ter, audāc-ter.
Third: the ending -iter is abstracted from the second type and attached to the bare root of an ...