| It is true that there are a few cases of a word "viri", which might have been the genitive of "virus". Nevertheless, the meaning of the word is not certain, at least in the examples that I have seen. Even if the word "viri" was really intended as the genitive of "virus", that is just another example of many cases when even the native speakers of Latin were not certain about the gender and declination class of certain seldom used words. Whoever has used "viri" as the genitive of "virus" was believing that it is a masculine word of the 2nd declension. Most attested uses of virus are consistent with it being a neuter of the 3rd declension (i.e. "virus" was used for the accusative case). The word virus cannot be a neuter of the 2nd declension (in that case it would have been "virum"). Actually it is possible that in very old Latin the word virus was indeed a masculine of the 2nd declension, like its cognate word in Greek, but due to its meaning as a name of a substance it was transferred to the neuter gender in the 3rd declension. Such interconversions of the words ending in -us between 2nd declension masculine, 3rd declension neuter and 4th declension masculine have happened for many words during the history of the Latin language, because even some native speakers guessed wrong the word class after hearing a rare word just a few times, and then others imitated them. |