I believe there are no exceptions to this rule. That's what I have always read, and I have never encountered any, neither in Greek nor in Latin, nor even in German.
There is an hypothesis about the cause of this phenomenon. Neuter words were historically limited to inanimate objects or things that cannot act. In a basic sentence, it was rarely or never the ...
As usual, to answer this question we need to step into our comparative linguistics-fueled time machine and go back to Proto-Indo-European times, so we can see what function the ending -a, which we know as a neuter plural ending, had in PIE.
In PIE, this ending -a (or rather *-(e)h₂) did not form plurals, but collectives. A collective refers to a group of ...
To answer your second question, this rule is completely exceptionless, not only in Latin but in all Indo-European languages (that is, those that have a neuter gender at all).
neuter gender always had identical nominative, accusative and vocative forms in all three numbers
Archaic Syntax in Indo-European
Tuomo Pekkanen's Ars Grammatica (a Latin grammar in Finnish) says that the second declension has three neuters ending in -us: vīrus, vulgus and pelagus.
They are only used in the singular, and accusative is exactly like the nominative (not -um).
I have no clue about the origin of these words.
I'm not sure if these words even have a similar history.
I'm not sure this covers all relevant ideas, so any addition/clarification is appreciated.
Four ideas that can help you:
Regarding logics as to certain types of nouns being predictably neuter by semantics alone, the main rule is... genders are arbitrary.
It is not completely random: women are feminine and men are masculine, but I'd trust grammar and ...
It depends on how much emphasis you put on "unambiguously refers to an individual human being". I don't know of any examples that are just like παιδίον or Mädchen. Several Latin grammars that I have looked at include short lists of neuter nouns that seem to have been used fairly regularly to refer to human beings, but it seems like most of these words did ...
Here’s a summary of what most authoritative Latin grammars say on the genitive singular ending of –io stems (Weiss 2009/2011: 222-223; Leumann 1977: 424-425; Sihler ). For the sake of simplicity and consistency, in my answer I use the periodization of Latin as used in Weiss (which is different from, for instance, Clackson and Horrocks or Meiser). Weiss has ...
Edgar H. Sturtevant's dissertation "Contraction in the case forms of the Latin io- and ia stems, and of deus, is, and idem" (1902) seems to have some relevant info, although I don't know if more has been discovered since then.
Contraction in the genitive singular
Sturtevant starts out by summarizing the genitive singular forms: he says that in early Latin, ...
There isn't really an answer to the "why" question beyond the fact that in Proto-Indo-European, some of the case endings for pronouns were different from those for nouns, for unknown reasons. Among these is the nom./acc. sg. neuter ending, which was *-d instead of *-m. This is clear from cognates in other languages, e.g. Sanskrit neuter demonstrative tad, ...
I was reading a new corpus study on gender assignment the other day - Hoffmann 2016 Gender in Latin and in language typology (in Latinitas Rationes, ed. P. Poccetti).
Based on two corpus studies, Hoffmann 2016 argues the following:
grammatical (morphological) gender assignment is predominant in Latin (71.4%), it includes gender assignment based on ...
A full table of "standard" (post-Augustan) -ius/-ium endings would be:
M SG M PL N SG N PL
NOM -ius -iī -ium -ia
GEN -iī -iōrum -iī -iōrum
DAT -iō -iīs -iō -iīs
ACC -ium -iōs -ium -ia
ABL -iō -iīs -iō -iīs
VOC -ī -iī -ium -ia
(O tempora! O mores! Why must upstanding citizens be ...
For the sake of completeness, it seems worth noting that there's one odd exception.
The gerund is a noun derived from a verb, representing an action (for example, volāndum "flying"). For the most part it acts as a regular second-declension neuter.
However, the gerund lacks a regular nominative, and instead uses the regular present active infinitive of the ...
Defining the vocative: something like "a form used for address"
I didn't give a definition of "vocative" in my original question, but it seems like it might be worthwhile, since there are a few constructions that look similar that we might want to distinguish.
It seems necessary to start with non-neuter -us nouns of the second declension like "Brutus" and "...
Actually Du Cange (Glossarium mediae et infimae latinitatis) records a lot of examples of the neuter form Pascha, -ae, which he seems to prefer.
"Orat. et prec. de Pascha annotino"
"Micrologus de Eccles. observ. cap. 56 : Romani Annotinum Pascha,
quasi anniversarium Pascha dicunt, quia antiquitus apud illos qui
in priori Pascha baptizati erant, ...
Bethlehem, n., indecl. Though a borrowing, clearly does not belong to the second declension. Note that there is also the alternative Bethlehemum, -i, which does belong to the 2nd.
I suspect there are no native Latin words, but it's just a suspicion with no etymological explanation. I'm certain other users could help with that. We have a number of experts in ...
Never realized that, but you have an example (nominative-only, though) in ecclesiastical Latin in the hymn Lauda Sion:
In hac mensa novi Regis
Novum Pascha novae legis
Phase vetus terminat
On this table of the [new] King,
Our new Paschal offering
Brings to end the olden rite.
So I did the exercise and searched for ...
The etymological explanation (which of course only takes the question a stage further back) is that in PIE, thematic inanimate nouns had the nom./acc. sg. ending *-om, while athematic inanimate nouns had a zero ending. The former became Latin second-declension neuters, the latter third-declension neuters.
This is only a partial explanation in that one might ...
I hadn't noticed this when I posted the question, but it turned out that the Wiktionary list that I mentioned in the original question contained at least one genuine word of interest. The word jūgerum/iūgerum is a second-declension form, but it seems that in the plural oblique cases we almost always see third-declension forms (jūgerum and jūgeribus; with ...
I extracted the dictionary file from Whitaker's Words (which admittedly has its flaws) while working on my (beta) Latin-English Dictionary.
Though I still haven't developed many advanced search tools, I now have the luxury of running any SQL query I have a mind to. The following query returns 6 results:
SELECT * FROM words WHERE part_of_speech = 'N' AND ...
I just found that Nouvelle méthode pour apprendre facilement la langue latine, by Claude Lancelot (? et al?), which I quoted in my previous question about Pascha, includes this word in a list of "those nouns which, as grammarians say, are not used in the plural, though we sometimes meet with examples to the contrary" (p. 150, A New Method of Learning with ...
There surely is an etymological reason, but unfortunately we don’t know it. Or there is no consensus about it.
All grammars mention the three second-declension neuters in -us, pelagus, virus and vulgus, and many go on explaining that pelagus is a recent Greek loanword which retained its gender (possibly influenced by mare), while virus has Indo-european ...