I pronomi relativi
A relative pronoun glues two sentences into one by replacing a repeated noun. Il libro è bello. Leggo il libro. → Il libro che leggo è bello = the book that I read is nice. Italian has three main relatives: che (subject or direct object — the workhorse), cui (after a preposition: with, of, to, for, from), and il quale / la quale / i quali / le quali (the formal alternative). Plus dove for places and quando for times. Big difference from English: you can't drop the relative — Italian ALWAYS uses one.
che — the all-purpose workhorse
che covers what English handles with 'who, that, which, whom' — when the relative is the SUBJECT or DIRECT OBJECT of the second clause. Il ragazzo che parla è Marco = the boy who is speaking is Marco (subject). La pizza che mangio è buonissima = the pizza that I'm eating is delicious (direct object). che is invariable — same form for masculine, feminine, singular, plural, person or thing. Never use it after a preposition. Never drop it: English allows 'the book I read' but Italian needs il libro che leggo.
cui — after every preposition
When you'd say 'with whom', 'of which', 'to whom', 'from which' — Italian uses a preposition + cui. Il libro di cui parlo = the book about which I'm talking / the book I'm talking about. L'amico a cui scrivo = the friend to whom I'm writing. La città in cui vivo = the city in which I live. La ragione per cui sono qui = the reason why I'm here. Like che, cui is invariable — gender and number are carried by context. Italian doesn't strand prepositions like English does ('the friend I wrote to') — the preposition stays in front: a cui scrivo.
il cui — whose
cui has one special trick: sandwiched between an article and a noun, it means 'whose'. Article + cui + noun, where the article agrees with the FOLLOWING noun (the thing possessed), not the owner. L'uomo il cui figlio studia qui = the man whose son studies here (il matches figlio, masculine singular). La donna la cui casa ho visitato = the woman whose house I visited (la matches casa, feminine singular). Lo scrittore i cui libri amo = the writer whose books I love (plural).
il quale — the formal alternative
il quale / la quale / i quali / le quali is a fancier substitute for che (when subject) or cui (with a preposition). It agrees in gender and number, which makes it useful for DISAMBIGUATING when che would be ambiguous. La sorella di Marco, la quale vive a Roma = Marco's sister, who lives in Rome (the la quale signals 'the sister' — not Marco — is feminine). With prepositions, the preposition combines with the article: del quale, della quale, al quale, nei quali. In speech, Italians overwhelmingly stick with plain che and cui; il quale shows up in writing, news, and formal speech.
dove and quando as relatives
dove = where (relative): La casa dove sono nato = the house where I was born. quando = when (relative): Il giorno quando ti ho visto = the day when I saw you (also fine and very common: il giorno in cui ti ho visto). These are everyday alternatives to in cui for places and times — both work, dove and quando are slightly more conversational.
