There are three neuters in the second declension ending in -us: virus, vulgus and pelagus. (See this previous question for origin and listing of such words.) My grammar tells me that these words are not used in the plural at all. I cannot believe that no one would have used these words in the plural through the millennia of Latin. If I want to scan my computer for viruses, describe how globalization brings the masses of different areas closer together, or sail the seven seas, I could use some plurals.

What are the plural forms of these three words? Are they found in all cases? Are they declined in the same way?

Neuters ending in -us typically have plurals -ora or -era (e.g. tempus–tempora and vulnus–vulneris). But these are in third declension and the -s is part of the stem. For my three words -s is (a part of?) the nominative case ending and they follow the second declension. Therefore the most appealing plural endings are -a, -orum and -is, but I have not seen these mentioned anywhere.

  • 1
    Since they're traditionally regarded as second-declension neuters, they would be vira, vulga, and pelaga; but their meanings don't really lend themselves to plurality, and there are other words that fill those voids.
    – Anonym
    Jul 4, 2016 at 19:21
  • @Anonym, why do the meanings not allow plurality?
    – Joonas Ilmavirta
    Jul 4, 2016 at 19:26
  • Because they're mass nouns. Pelagus amo means 'I love the sea (in general)', whereas mare amo means 'I love a certain sea/the specified sea'
    – Anonym
    Jul 4, 2016 at 19:30
  • @Anonym, mass nouns can be pluralized, although it is not very common. See TKR's answer for an attested example of a plural of pelagus.
    – Joonas Ilmavirta
    Jul 4, 2016 at 19:34

2 Answers 2


Acc. pl. pelagē occurs in Lucretius, De Rerum Natura 6.619:

at pelage multa et late substrata videmus

This is simply the Greek plural: the word is a loan of Greek πέλαγος, whose nom./acc. pl. is πελάγη.

A Packard search finds no results for vira, virora, vulga, vulgora.


It seems there are many theories, among them viri, virora, and virus. (The point of the article is that it's pointless to try to figure it out.)

Here, however, is a refutation of the article linked above that contains an argument based on what seems to be solid linguistics ("seems" because it's been so long since I studied linguistics that I can't really tell anymore) and asserts that the plural has to be vira.

(Sorry about the other answer, which I've deleted—I forgot momentarily how to use a dictionary and was taking genitive as plural.)

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    That first article seems a bit silly to me. Virus does indeed look a bit like vir when declined, but the length of the -i- is different. And sometimes different words become the same when suitably declined. Declined forms are attested, so guessing whether it should be fourth or third declension has little support. The second article looks much more credible.
    – Joonas Ilmavirta
    Jul 4, 2016 at 15:07
  • Yeah, that was my sense, too. Jul 4, 2016 at 15:11

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