English has one 'you'. Italian, like Persian with «تو» and «شما», has an informal and a polite form. Tu is for friends, family, children and people your own age in casual settings. Lei is for strangers, shop staff, officials, older people and most professional situations.
The key difference: the verb
Here is where Italian differs from Persian. Persian «شما» takes a plural verb; Italian Lei takes the third-person singular — the same form as 'he/she'. So 'How are you?' is Come stai? with tu but Come sta? with Lei. In writing, Lei is often capitalized to show respect.
Ciao Marco, come stai? — Buongiorno, signora Rossi, come sta?
Same question, two registers: stai (tu) and sta (Lei).
- Talking to a group? Use voi for everyone, formal or not: Come state?
- Not sure? Start with Lei. It is never rude, and Italians will tell you if they prefer tu.
- The switch is often offered with: Possiamo darci del tu? — Shall we use tu?