In short

Italian has eight everyday prepositions: di, a, da, in, su, con, per, tra/fra. Five of them - di, a, da, in, su - are forced to fuse with a following definite article into a single word (a + il = al, di + lo = dello, in + le = nelle). Writing a il or di lo is never an option.

The rule

A preposition is a small linking word that sits before a noun. Choose it for the meaning first, then deal with the article.

Step 1 - Pick the preposition for the meaning you want. The eight core ones:

• di = of (belonging, origin, material) - la casa di Anna, Sono di Roma, un tavolo di legno
• a = to / at (destination and position, cities, people you speak to) - Vado a Roma, Sono a casa
• da = from (where you come from), at someone’s place, since - Vengo da Milano, Vado dal medico
• in = in / to (countries, regions, many enclosed places) - Vivo in Italia, Sono in banca
• su = on, about - Il libro è sul tavolo, un film su Napoli
• con = with - Esco con Maria
• per = for, in order to, and the destination of a vehicle - un regalo per te, il treno per Roma
• tra / fra = between, among; in (future time) - tra i due, fra due ore

Step 2 - Ask: is a definite article coming next? If the noun has no article, the preposition stays alone and nothing happens: a casa, in Italia, di legno, con Maria. Contraction also never happens with the indefinite article: di un amico, a una ragazza, su un tavolo stay as two words.

Step 3 - If a definite article is coming, check whether your preposition contracts.

• di, a, da, in, su -> contraction is compulsory, always one word.
• con -> optional, and only col (con + il) and coi (con + i) are still normal; modern writing prefers con il, con i.
• per, tra, fra -> never contract: per il treno, tra le case.

Step 4 - Build the fused form. The article keeps its usual selection rules (il / lo / l’ / la / i / gli / le, see step 1 of the path) - pick it exactly as you would without a preposition, then glue it on. di becomes de-, in becomes ne-, and the others keep their letter: de + lo = dello, ne + gli = negli, su + il = sul, a + la = alla.

So: if the noun takes lo (lo stadio), every contraction is built on lo -> allo stadio, dello stadio, nello stadio. Get the article right and the contraction is automatic.

Note: di + article before a noun can also mean “some” (del pane = some bread). That is the partitive, a separate job for the same forms - see step 27.

Forms & patterns

The full table. The first five rows are compulsory; the last three show what stays apart.

Which preposition for which place - the choice English speakers get wrong most often:

Examples

Common mistakes

• Vado a il cinema -> Vado al cinema - with di, a, da, in, su the fusion is compulsory; two separate words is simply not Italian.
• Vado al stadio -> Vado allo stadio - stadio takes lo, so the contraction must be built on lo: a + lo = allo.
• Sono in Roma -> Sono a Roma - cities take a; in is for countries and regions (in Italia).
• Vado a Marco -> Vado da Marco - going to a person (or their home, shop, surgery) is da, never a.
• Vado nel centro -> Vado in centro - these fixed expressions carry no article, so there is nothing to contract (same with in banca, a casa, a scuola).

Tips

• The five that contract are the five shortest: di, a, da, in, su. con, per, tra/fra are longer and stay free - a rough but reliable memory hook.
• Never memorise 35 separate words. Choose the article the noun needs, then fuse: lo zaino -> nello zaino, gli amici -> degli amici, l’acqua -> dell’acqua.
• di and da look alike and are constantly swapped. di = “of” (la casa di Anna - whose), da = “from” (vengo da Roma - where out of) and “at someone’s” (dal medico).
• tra and fra mean exactly the same thing: choose whichever avoids an ugly echo with the next word - fra tre giorni (not tra tre), tra fratelli (not fra fratelli).