On the whole, Italian is a mighty regular language. Of course it has its irregularities, but many fewer than, say, English. Plurals, for example, are largely predictable, but with some curious exceptions. The masculine noun bue (ox or sometimes, by extension, a dolt) seems to call for the plural form *bui, but it's not so; it's buoi. Dio (god), becomes dei rather than *dii. The very ordinary word uomo (man), yields the extraordinary plural uomini -- which is strange indeed except to oldsters who remember homo, hominis from their high school Latin class. The word for wing is ala and, if Italian were law-abiding, its plural should be *ale but instead it's ali. Similarly, arma should yield *arme, but doesn't; it's armi. Eco has the plural echi, which seems normal, except that the singular is feminine and the plural masculine, so la eco but gli echi. Some words, conversely, have masculine singulars but feminine plurals: most notably, uovo (egg) which becomes uova rather than *uovi, while dito (finger) becomes the odd masculine dita. Paio (pair) is similar; its plural is paia. Il riso (a laugh) has the plural le risa. There's the same gender switch with the truly curious word for ear -- orrechio becomes orecchie. There are a few words with two slightly different plural forms, many of them words for parts of the body, such as braccio (arm) which can become bracci or braccia; ciglio (eyebrow) , which has plurals in cigli and ciglia; ginocchio (knee) which can be either ginocchi or ginocchia, and osso (bone) which can be ossi or ossa. I'm fond of muro (wall) the regular plural of which is muri (the walls of a house) but also yields the irregular plural mura, which refers to the fortifications or walls of a city.