Se o bilhete for inválido, não entras no cinema.

If the ticket is invalid, you cannot enter the cinema.

Breakdown of Se o bilhete for inválido, não entras no cinema.

• ser: to be
• tu: you
• em: in
• não: not
• entrar: to enter
• se: if
• o bilhete: the ticket
• o cinema: the cinema
• inválido: invalid

Questions & Answers about Se o bilhete for inválido, não entras no cinema.

Why is the verb ser in its subjunctive form for instead of the indicative é in the clause Se o bilhete for inválido?

In Portuguese, when you talk about a possible or future situation introduced by se (“if”), you normally use the present subjunctive in the “if” clause (protasis). It expresses uncertainty: you don’t know yet whether the ticket will be invalid. Using é (indicative) would sound more like stating a general fact or habit (“If the ticket is invalid, then…”) rather than a specific future possibility.

How do you form for, and why not some other subjunctive?

For is the 3rd person singular present subjunctive of ser. You form it from the first-person singular indicative sou, drop the o, and add the subjunctive endings:
-ar verbs: e, es, e, emos, eis, em
-er/-ir verbs: a, as, a, amos, ais, am
So for ser you get: que eu seja, que tu sejas, que ele/ela/você seja – but this is the irregular “seja” pattern. Portuguese also has an older literary form: que eu for, que tu fores, que ele for. In spoken European Portuguese, for is common too for formal or future conditions.

Why does the main clause use não entras (present indicative) instead of a future tense like “won't enter”?

In a real (possible) future condition, Portuguese uses present subjunctive in the “if” part and present indicative in the result part. The present indicative carries the future meaning:
“Se o bilhete for inválido, não entras no cinema.”
= “If the ticket turns out to be invalid, you don’t (will not) get in the cinema.”
Using a future form (e.g. não entrarás) is grammatically correct but more formal or literary.

What person and pronoun does entras refer to?

Entras is the second-person singular present indicative of entrar (tu). It literally means “you enter.” European Portuguese commonly uses tu with friends or family. If you wanted to use você, you’d say (você) não entra (he/she/you‐formal).

Can I use caso instead of se here?

Yes. Caso also introduces conditions and almost always requires the subjunctive in the protasis:
“Caso o bilhete for inválido, não entras no cinema.”
The nuance is subtle; caso can sound slightly more formal or written than se.

Why is it no cinema and not ao cinema?

• Entrar (to enter) pairs with em
  • definite article (“in/into”). Em + o = no, so no cinema means “into the cinema.”
• Ir (to go) pairs with a
  • article (“to the cinema”) → ao cinema.
    So you enter no cinema, but you go ao cinema.

Could I invert the clauses: Não entras no cinema se o bilhete for inválido?

Yes, you can place the result clause first without changing meaning. When the if-clause follows, you don’t need a comma:
“Não entras no cinema se o bilhete for inválido.”
Both word orders are natural.

Why do Portuguese speakers say bilhete here, and is ingresso wrong?

In Portugal, bilhete is the standard word for “ticket” (train ticket, cinema ticket, etc.). Ingresso is more common in Brazilian Portuguese for event or movie tickets. In Europe you might understand ingresso, but you’ll hear bilhete far more often when buying entry.

Can I replace the result clause with a command, like não entres no cinema?

You could, but it changes the meaning.

• Não entras no cinema. is a statement: “you won’t get in.”
• Não entres no cinema. is an order: “don’t go/enter the cinema!”
  Use the imperative form entres only when you want to forbid someone from entering.