vitium

Vitium, vitii is second declension neuter, and its core sense is a flaw: a crack in a wall, a corruption in a text, a hole in an argument. The moral sense, "vice", is a narrowing of that, and the ethical writers set it squarely against virtus.

Mind the false friend. English vice always implies wickedness, whereas a vitium in a technical passage may be nothing worse than a structural defect. In augury vitio creatus describes a magistrate elected under a faulty auspice, a use that says a good deal about how Romans thought about procedure. The verb vitiare and English vitiate keep the neutral sense intact.