[nerdponx]

Not so fast.

"virus" is a nonstandard Latin mass noun. It's neuter, but uses the 2nd declension masculine nominative, and being a mass noun it had no plural form in classical Latin. However if you wanted to give it a plural form, the grammatically correct plural would be "vira". This construction would be analogous to "fishes" or "waters" in English.

"surplus" comes to us via Old French, so its plural perhaps should be whatever plurals were in Old French. However it also originates in Latin as "superplus", which is the prefix "super" + the adjective "plus". The word "plus" itself is also irregular. Its masculine or feminine nominative plural is "plures", and its neuter nominative plural is "plura".

I admit that "superplodes" is pretty fun to say.

[thaumasiotes]

> The word "plus" itself is also irregular. Its masculine or feminine nominative plural is "plures", and its neuter nominative plural is "plura".

What's irregular about that?

[nerdponx]

Well, nothing technically, from what Latin I remember. I meant it in the not-technical sense that the nominative form is different from the word stem and it looks superficially like a standard 1st/2nd declension adjective.