opera

This week reminds me of a favorite subject of mine: incorrect Latin plurals. Opus 'work' and *opii (correct opera), virus 'poison; slime' and *virii (there is no correct plural, the word only occurs in Latin as a singular), octopus and *octopi (correct Greek octopodes), syllabus and *syllabi (correct syllabus), same with apparatus and *apparati (apparatus).

In english, the plurals I would use are: opus and opuses (opera has a new specialized meaning in English), virus and viruses, octopus and octopuses, etc.

Ceci n'est pas un seing.