Relative Pronoun Cui: With Prepositions | Italian Grammar

In Italian, the relative pronoun che does the work of English "that/which/who" — but only as a subject or direct object. The moment a preposition enters the picture (about which, with whom, from which, in which), Italian hands the job to a different word: cui. This page is about that word. By the end you will know exactly when to reach for cui, how to combine it with every Italian preposition, and how to wield its most distinctive use: the construction il cui / la cui / i cui / le cui, which means "whose" — and which inflects in a way that surprises every English speaker on first encounter.

Cui is invariable. It does not change for gender (il cui, la cui are not different forms of cui — see section 4) and it does not change for number. The same four letters cover masculine, feminine, singular, plural — every time. What does change is the preposition placed in front.

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The single rule that solves 80% of cui usage: after any preposition, use cui, never che. Il libro che leggo (the book I read — direct object, che); Il libro *di cui ti parlo (the book I'm telling you about — preposition + *cui). Mix this up and your Italian will sound subtly broken to a native speaker, even when they understand you.

1. Why Italian needs cui

English relativizes prepositional phrases in two ways: stranding (the book I'm talking about) or pied-piping (the book about which I'm talking). Stranding is the everyday choice in conversation; pied-piping sounds formal. Italian has no stranding. The preposition must travel together with its relative pronoun, sitting in front of it, the way English does only in formal writing. And because che can never appear after a preposition, Italian uses cui for exactly this slot.

This is the architectural reason cui exists: Italian needs a relative pronoun that can stand after a preposition, and che is not it. Once you internalise this, the rest of the system unfolds naturally.

Il libro di cui parlo è un romanzo di Calvino.

The book I'm talking about is a novel by Calvino.

La persona a cui ho scritto non mi ha ancora risposto.

The person I wrote to hasn't replied to me yet.

L'amico con cui esco stasera abita a Milano.

The friend I'm going out with tonight lives in Milan.

Notice how all three English translations strand the preposition (about, to, with), while the Italian originals place the preposition before cui. Italian word order on this point is fixed; English has options.

2. Cui with every common preposition

Cui combines with all the simple prepositions: a, di, da, in, su, per, con, tra/fra, plus locative compounds like sotto, sopra, dentro, davanti a, dietro a, vicino a. Here are the most common combinations, each with an example.

Combination	Meaning	Example
a cui	to/at which, to whom	la persona a cui ho scritto
di cui	of/about which, of whom	il libro di cui parlo
da cui	from which, from whom	la città da cui vengo
in cui	in which, in whom	l'epoca in cui viveva Dante
su cui	on/about which	l'argomento su cui discutiamo
per cui	for/because of which, why	il motivo per cui sono venuto
con cui	with which, with whom	la penna con cui scrivo
tra cui / fra cui	among which	cinque candidati, tra cui Marco
sotto cui	under which	il tavolo sotto cui era nascosto

A handful of small but real points to notice:

No article fusion with cui. Unlike full nouns (del libro, al teatro), cui never fuses with di or a: it stays di cui, a cui. The articulated forms del/al/dal/nel/sul are reserved for il quale (see Il Quale).
The preposition cannot move. Il libro cui parlo di is impossible — cui and its preposition are inseparable.
Per cui = "why" in everyday speech: Il motivo per cui sono qui / La ragione per cui non posso venire. This is the standard way to say "the reason why" in Italian.

La città da cui vengo è piccola, ma ha un porto bellissimo.

The city I come from is small, but it has a beautiful harbour.

L'argomento su cui dobbiamo discutere è delicato.

The topic we have to discuss is delicate.

Il tavolo sotto cui era nascosto il gatto è in cucina.

The table the cat was hidden under is in the kitchen.

È venuta tutta la famiglia, fra cui anche mio nonno.

The whole family came, including my grandfather.

3. Time and place: in cui and da cui

Two combinations deserve special attention because they cover situations where English speakers expect when or where.

Time → in cui. Italian uses in cui for relative clauses about time: il giorno in cui (the day when), l'anno in cui (the year when), l'epoca in cui (the era in which). Note that English "when" maps to Italian in cui in a relative clause, not to a relative quando. There is also an informal alternative che: il giorno che ti ho conosciuto — common in speech, perfectly acceptable.

Ricordo ancora il giorno in cui ci siamo conosciuti.

I still remember the day we met.

L'anno in cui sono nato è stato un anno di grandi cambiamenti.

The year I was born was a year of great changes.

Place → in cui, a cui, da cui — but for a simple location, dove is more natural. La città in cui vivo and La città dove vivo are equivalent; the second is more conversational. Reserve in cui / a cui / da cui for cases where you need a specific preposition: La città da cui vengo (origin) cannot be replaced with dove, since da has a directional meaning dove does not carry.

L'ufficio in cui lavoro è in centro.

The office I work in is downtown.

La spiaggia da cui siamo partiti era affollata.

The beach we set off from was crowded.

4. The "whose" construction: il cui / la cui / i cui / le cui

This is where cui becomes interesting. To express English "whose" — the genitive relative — Italian uses a structure that surprises learners on first encounter:

definite article + cui + noun

The article is determined by the noun that follows cui, not by the antecedent of the relative clause. This is the inverse of how English speakers tend to expect things.

Structure	Italian	English
masc. sg. possession	lo scrittore il cui romanzo vinse il premio	the writer whose novel won the prize
fem. sg. possession	la donna la cui figlia è attrice	the woman whose daughter is an actress
masc. pl. possession	gli studenti i cui voti sono alti	the students whose grades are high
fem. pl. possession	le persone le cui idee mi piacciono	the people whose ideas I like

In lo scrittore *il cui romanzo, the article *il is masculine singular because romanzo is masculine singular — even though scrittore (the possessor) happens also to be masculine singular here. The agreement crosses the relative pronoun and lands on the thing being possessed. Make the possessor feminine and the article does not change:

La scrittrice il cui romanzo vinse il premio è italiana.

The writer (f.) whose novel won the prize is Italian. (Article 'il' agrees with 'romanzo', not 'scrittrice'.)

Lo scrittore le cui poesie sono famose vive a Roma.

The writer whose poems are famous lives in Rome. (Article 'le' agrees with 'poesie', f. pl.)

Una città la cui storia risale a duemila anni fa.

A city whose history goes back two thousand years.

I miei vicini, i cui figli giocano sempre in giardino, sono molto simpatici.

My neighbours, whose kids are always playing in the garden, are very nice.

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The trick to mastering il cui is to think of cui itself as invisible to agreement — the article and the noun behave like a normal article-noun pair (il romanzo, le poesie, i figli), and cui simply slots between them to mark the possessive relationship. Read il cui romanzo as "il romanzo, of which" — the article belongs to romanzo.

A subtlety: when cui is the object of a preposition that already governs the possessed noun, the article goes after the preposition: un autore alle cui opere ci ispiriamo (an author whose works inspire us — a + le + cui + opere, with a + le fusing into alle). This is a B2/C1 construction; B1 learners can recognise it without producing it.

5. Comma rules: defining vs non-defining clauses

Like English, Italian distinguishes two kinds of relative clauses, and the punctuation matters:

Defining (restrictive): identifies the antecedent. No commas. La persona di cui ti parlavo è arrivata — of whom I was telling you singles out a specific person.
Non-defining (non-restrictive): adds extra information. Commas. Mio fratello, di cui ti ho parlato spesso, abita a Torino — the relative clause is parenthetical.

In speech, the non-defining clause is set off by a slight pause; in writing, by commas. This is the same convention as English, so it transfers cleanly.

I miei genitori, ai quali devo molto, vivono ancora insieme.

My parents, to whom I owe a great deal, still live together. (Non-defining — note the commas.)

La ragazza con cui esco si chiama Sofia.

The girl I'm going out with is called Sofia. (Defining — no commas, identifies which girl.)

6. Cui vs del quale / al quale: when to switch

Every cui combination has a longer, more formal twin: del quale, al quale, dal quale, nel quale, sul quale, per il quale, con il quale. These inflect in gender and number to agree with the antecedent. Use them when:

Formal or written register demands a more polished feel.
Disambiguation: when cui alone would leave the antecedent unclear, il quale forces a particular reading via gender and number.
After certain conjunctions where cui sounds awkward in elevated prose.

For most everyday Italian, cui is the right choice — shorter, faster, unmarked. Reach for il quale deliberately, not by default. See Il Quale: Formal Alternative for the full treatment.

Il professore con cui ho studiato è in pensione.

The professor I studied with is retired. (Everyday Italian — 'con cui'.)

Il professore con il quale ho studiato è in pensione.

Same meaning, more formal. ('con il quale' — written/academic register.)

7. Per cui in idiomatic use

A short note on per cui, which has gone beyond its literal meaning ("for which") to become a sentence connector meaning "and so / therefore" in informal speech:

Era tardi, per cui sono andato a casa.

It was late, so I went home. ('per cui' as a conjunction — colloquial)

This is grammatical in conversation but should be replaced by quindi or per questo in writing. Treat it as a conversational tic worth recognising but not over-using.

8. Common mistakes

The errors below are predictable transfers from English habits and from confusion with the simpler relative che. Each pair shows a wrong sentence and the corrected version.

❌ Il libro di che parlo è bellissimo.

Incorrect — 'che' cannot follow a preposition. Use 'cui'.

✅ Il libro di cui parlo è bellissimo.

The book I'm talking about is wonderful.

❌ La donna la cui marito è medico abita qui.

Incorrect — the article must agree with 'marito' (m. sg.), not with 'donna'. The possessor's gender is irrelevant.

✅ La donna il cui marito è medico abita qui.

The woman whose husband is a doctor lives here.

❌ Il ragazzo io parlo a abita a Roma.

Incorrect — Italian cannot strand the preposition. The relative clause must use 'a cui' before the verb.

✅ Il ragazzo a cui parlo abita a Roma.

The boy I talk to lives in Rome.

❌ La città in che vivo è grande.

Incorrect — 'in che' is impossible. Use 'in cui' or, more naturally, 'dove'.

✅ La città in cui vivo è grande.

The city I live in is big. (Or: 'La città dove vivo è grande.')

❌ Il motivo perché sono venuto è importante.

Incorrect — 'perché' means 'because/why' in questions, not in relative clauses. Use 'per cui'.

✅ Il motivo per cui sono venuto è importante.

The reason why I came is important.

❌ Lo scrittore di cui libro ho letto è famoso.

Incorrect — for 'whose', use the construction 'il cui' (article + cui + noun), not 'di cui + noun'.

✅ Lo scrittore il cui libro ho letto è famoso.

The writer whose book I read is famous.

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If you are unsure whether a relative clause needs che or cui, ask: is there a preposition involved? If yes, cui. If no, che. The single exception is the il cui possessive, which is cui preceded by an article rather than a preposition — but you'll recognise it because there's a noun immediately after.

Key takeaways

Cui is the relative pronoun used after any preposition: a cui, di cui, in cui, su cui, per cui, etc.
Cui is invariable — it never changes for gender or number.
For "whose", use il cui / la cui / i cui / le cui — the article agrees with the possessed noun, not the possessor.
Italian cannot strand prepositions: the preposition must precede cui directly.
Cui is the default everyday choice; il quale is the formal/clarifying alternative.
Per cui doubles as the standard way to say "the reason why" in Italian.

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