Learn Hardcore Portuguese (Portugal): Se a criança gritar no teatro, o senhor, por favor, leve‑a ao corredor. - If the child shouts in the theatre, sir, please take her to the aisle.

Because Portuguese uses the future subjunctive after the conjunction se when talking about a possible future event. The verb gritar in the future subjunctive (3rd person singular) happens to look the same as the infinitive: gritar.

Future subjunctive: gritar, gritares, gritar, gritarmos, gritardes, gritarem
Present subjunctive: grite, grites, grite, gritemos, griteis, gritem

So here it must be future subjunctive, not present subjunctive.

How can I tell that gritar here isn’t just the infinitive?

Two clues:

The structure se + verb that refers to a future condition calls for the future subjunctive, not an infinitive.
There’s an explicit subject (a criança) before the verb, so the verb is finite. Infinitives normally come after prepositions (e.g., para gritar, sem gritar), not directly after se in this meaning.

Why is it leve and not leva?

Because o senhor is a formal way to say “you” that takes third‑person verb forms. The Portuguese affirmative imperative for “you (formal)” uses the present subjunctive: leve. If you were speaking to an informal tu, you’d say leva.

What exactly does o senhor mean here? Is it just “sir”?

With the article, o senhor functions like a formal second‑person pronoun (“you, sir”) and requires third‑person verb agreement: o senhor leve.
Without the article, Senhor, … is a vocative (“Sir, …”) used just to address someone. In the sentence, o senhor is the subject-like form meaning “you” in a polite way.

Can I use você or tu instead of o senhor? What changes?

Yes:

Você (less formal in Portugal, can sound brusque with strangers): Se a criança gritar no teatro, você, por favor, leve‑a ao corredor. (still leve, third person)
Tu (informal): Se a criança gritar no teatro, por favor, leva‑a ao corredor.

In Portugal, o senhor / a senhora is the safest polite option with unknown adults.

Why is the pronoun a used, and not ela or lhe?

a is the unstressed direct‑object clitic for “her/it” (feminine singular). It attaches to the verb: leve‑a = “take her.”
ela is a stressed pronoun typically used as a subject or after prepositions (com ela, para ela). Using leve ela is common in Brazilian speech but non‑standard in European Portuguese.
lhe is an indirect‑object clitic (“to him/her”), so it would mean “take to her,” not “take her.”

Why is the pronoun attached after the verb with a hyphen (leve‑a)? Could it go before?

In European Portuguese, affirmative imperatives take clitic pronouns after the verb with a hyphen (enclisis): leve‑a. With negation or certain triggers, the pronoun goes before (proclisis):

Affirmative: Por favor, leve‑a ao corredor.
Negative: Por favor, não a leve ao corredor.

Why is it leve‑a and not levá‑la?

The forms ‑lo/‑la/‑los/‑las (with an accent on the verb) appear when you attach the object pronoun to a verb that ends in ‑r, ‑s, or ‑z, or to an infinitive/gerund:

Infinitive: levar + a → levá‑la
Imperative (tu): leva + a → leva‑a (no accent)
Imperative (o senhor/você): leve + a → leve‑a (no accent)

Here the verb is leve (ends in ‑e), so it’s simply leve‑a.

Does a here mean the child is a girl?

Not necessarily. Criança is grammatically feminine in Portuguese, regardless of the child’s sex. The pronoun agrees with the noun’s grammatical gender:

Referring to a criança → leve‑a
Referring to o menino → leve‑o

What do no and ao stand for, and what’s the difference?

They’re contractions:

no = em + o (“in/on the”): no teatro = “in the theatre”
ao = a + o (“to the”): ao corredor = “to the corridor/hallway”

Is ao corredor the most natural phrasing in Portugal for a theatre context?

It’s fine. Other natural options:

para o corredor (to the corridor)
lá fora (outside)
para o átrio / para o foyer (to the lobby/foyer) Note: corredor can also mean the aisle between seats, depending on context.

Where can I put por favor in this sentence?

Flexible positions, all correct with appropriate commas:

Por favor, o senhor leve‑a ao corredor.
O senhor, por favor, leve‑a ao corredor.
O senhor leve‑a ao corredor, por favor.

Are the commas used correctly?

Yes. In Portuguese:

A comma separates the initial se‑clause from the main clause.
por favor is set off with commas as a parenthetical.
o senhor here functions as the subject (formal “you”), not merely a vocative. If it were a pure vocative, you’d typically see Senhor, … (without the article).

Can I add então (“then”) after the comma?

Yes, for emphasis or clarity: Se a criança gritar no teatro, então o senhor, por favor, leve‑a ao corredor. It’s optional; many speakers omit então.

How would this change with plural children or if addressing multiple people?

Plural children: Se as crianças gritarem no teatro, o senhor, por favor, leve‑as ao corredor.
Addressing multiple people (formal): Se a criança gritar no teatro, os senhores, por favor, levem‑na ao corredor.

Do we always use the future subjunctive after se?

Use it when the se‑clause refers to a real/possible future situation: Se a criança gritar, … For hypotheticals considered unlikely, use the imperfect subjunctive: Se a criança gritasse, … For general truths/habitual actions, the present indicative is possible: Se a criança grita, … (though you’ll also hear the future subjunctive in many such cases).