Why 'Vir' is the only word of 2nd declension with -ir ending?

1. Why is the plural of virus not viri?
2. Is vir second declension?
3. What does Latin word vir mean?
4. Is it Virii or viruses?

Why is the plural of virus not viri?

The plural virii, though common, is based on a misunderstanding of Latin. In classical Latin, virus appears to be a singulare tantum without any attested plural. If virus were a masculine 2nd declension noun, it would form its plural with a singular -i as viri.

Is vir second declension?

Second-declension noun (nominative singular in -r). The genitive plural may also be virum, virûm.

What does Latin word vir mean?

(vɪər) Latin. noun. husband (used chiefly in the legal phrase et vir)

Is it Virii or viruses?

Viruses is the only way to make the noun virus plural. Confusion arises over the plural of virus because people mistakenly believe that viri or virii is its Latin plural form, (in the same way that fungus, cactus, and hippopotamus become fungi, cacti, and hippopotami).