I pronomi relativi
Relative pronouns let you weld two sentences into one: The book. I read it. → The book I read. Italian has five tools. che is the universal subject- or direct-object relative ('who / which / that'), invariable, used in 80% of cases. cui is the relative used after a preposition ('to whom', 'about which', 'for which'): a cui, di cui, per cui, in cui. il quale / la quale / i quali / le quali is a more formal alternative that AGREES with its noun — handy for disambiguation. chi = 'the one who' / 'whoever' (people only, no antecedent). quanto = 'all that' / 'as much as' — the neuter 'everything that'.
Che — the workhorse subject/object relative
che is invariable and works for both subjects and direct objects, animate or inanimate, masculine or feminine, singular or plural. SUBJECT: Il ragazzo che parla è Marco. = the boy who is speaking is Marco. OBJECT: Il libro che leggo è bello. = the book (that) I'm reading is good. La donna che ho visto = the woman (whom) I saw. Le città che ho visitato = the cities (that) I visited. NEVER use che after a preposition — that's cui's job. And in compound tenses, the past participle agrees with che when che stands for a feminine or plural direct object: i libri che ho letti (or, more commonly, letto).
Cui — the prepositional relative
When the relative pronoun follows a preposition, use cui (invariable). Common combinations: a cui = to whom / to which, di cui = of whom / of which / about which, per cui = for which / for whom, in cui = in which / when (after a noun of time), con cui = with whom / with which, da cui = from whom / from which, su cui = on which. L'uomo a cui parlo = the man to whom I'm speaking. Il libro di cui ti ho parlato = the book I told you about. L'anno in cui sono nato = the year in which I was born. La ragione per cui sono venuto = the reason for which I came. With possessives: il cui / la cui / i cui / le cui + noun = 'whose': lo scrittore il cui libro ho letto = the writer whose book I read (article agrees with the POSSESSED noun, not the possessor — like English 'whose').
Il quale — the formal alternative
il quale, la quale, i quali, le quali is a longer, more formal substitute that AGREES in gender and number with its antecedent. It can replace che (less common, more formal) or cui (common after prepositions for clarity). Useful when che would be ambiguous: Ho conosciuto la sorella di Marco, la quale vive a Roma. — la quale clearly points to the SISTER, not Marco; che would be ambiguous between them. After prepositions, all forms combine: al quale, alla quale, ai quali, alle quali; del quale, della quale; dal quale, etc. L'uomo al quale ho parlato = the man to whom I spoke (= a cui). Use sparingly in everyday speech — it sounds bureaucratic — but it's everywhere in writing and journalism.
Chi — 'the one who' / 'whoever'
chi is a relative pronoun ONLY for people, with NO antecedent — it bundles 'the person who' or 'whoever' into one word. It always takes the third-person singular verb. Chi dorme non piglia pesci. (proverb) = he who sleeps catches no fish. Chi parla troppo sbaglia spesso. = whoever talks too much often makes mistakes. Cerco chi possa aiutarmi. = I'm looking for someone who can help me. After prepositions, chi works the same: a chi vuoi parlare? = to whom do you want to speak? (interrogative). Per chi suona la campana? = for whom the bell tolls? Don't confuse chi (relative-with-no-antecedent / interrogative) with che (relative WITH antecedent).
Quanto — 'all that' / 'as much as'
quanto as a relative means 'all that' / 'everything that' / 'as much as' — neuter, no antecedent needed. Ho fatto quanto potevo. = I did all that I could. Mi ha detto quanto sapeva. = he told me everything he knew. Prendi quanto ti serve. = take as much as you need. Variants: tutto quanto = absolutely everything; tutto quello che is a synonym (same meaning, more common in speech). The agreeing forms quanto, quanta, quanti, quante also exist as quantity adjectives (quante mele vuoi? = how many apples?), but as a RELATIVE pronoun, quanto stays neuter.
