3rd declension accusative plurals

Question

I am being driven round the bend by people’s insistence on “playing Horace on original instruments” and I need some way out of the morass.

At school the 3rd declension accusative plural ending was -es and that was that. Rudyard Kipling uses this - maerentes amicos and so on - which I suppose shows that I am a contemporary of Kipling. I need to de-obsolesce, because I am getting tired of asking “what is this genitive singular doing in maerentis amicos?”.

Gildersleeve and Lodge say for vowel stems in i (57.5) that “-is is found frequently in the classical period along with the later termination -es, which supplants -is wholly in the early empire”. They also add that polysyllabic stems in nt are in a very real sense stems in i (54 though their wording is more Victorian than mine).

Now, given that one has to face texts which have intruded the loathsome -is, what are the rules?

My first guess was that one could say simply “anything that has a genitive plural in -ium will have its accusative plural written as -is.

Is this a complete and sufficient rule?

Answer 1

Unfortunately, there doesn't seem to be any rule that is both simple and complete. This might be the reason why so many modern editions normalize spellings by replacing accusative plural -īs with -ēs (unless the word has an accusative singular in -im).

Your suggestion that accusative plural -īs is possible if the word has a genitive plural ending in -ium is a good rule of thumb, but has exceptions. As per the answer I posted in reply to the prior question Constantis vs. constantes et similia, Allen and Greenough §77, §117 and §118 have some information on the use of this ending (although some of what this source says about etymology is out of date).

I think that some words may have an attested accusative plural in -īs but no attested genitive plural in -ium. For example, comparative adjectives generally are inflected as consonant stems (an exception to the general tendency for Latin third-declension adjectives to be i-stems), but the non-neuter accusative plural of comparatives is sometimes found ending in -ōrīs (as in the example of peioris asked about in this question). I haven't seen a corresponding genitive plural peiōrium used anywhere in ancient texts.