Se o interfone tocar, a moça da portaria pode abrir o portão.

Because after se meaning if, Portuguese often uses the future subjunctive when talking about a possible future event:

• Se o interfone tocar... = If the intercom rings...

For many regular verbs, the future subjunctive looks identical to the infinitive, so tocar here is not the infinitive in function, even though it has the same form.

Compare:

• Se ele vier, eu aviso. = If he comes, I’ll let you know.
• Se chover, ficamos em casa. = If it rains, we stay home.

So tocar is correct because the sentence is about something that may happen in the future.

You know from the structure of the sentence.

After se introducing a future condition, Portuguese normally wants the future subjunctive:

• Se o interfone tocar...
• Se ele chegar cedo...
• Se você puder...

Even though tocar, chegar, and puder may resemble dictionary forms in some cases, their role in the sentence is verbal and conditional, not infinitive.

A clue is that the clause already has a subject:

• o interfone = subject
• tocar = verb

So this is not to ring, but if it rings.

In this sentence, se most naturally means if.

• Se o interfone tocar... = If the intercom rings...

In real-life context, English might sometimes translate this kind of sentence more naturally as when the intercom rings, especially if the speaker expects it to happen. But grammatically, se is the normal word for if.

If Portuguese wanted a clearer when, it would typically use quando:

• Quando o interfone tocar... = When the intercom rings...

So se keeps the idea conditional.

Interfone is the intercom, especially the building entry intercom used to contact residents or staff.

In Brazil, this is very common in apartment buildings, gated buildings, and condominiums. So o interfone tocar means the entry intercom is ringing.

Related words you may also hear:

• campainha = doorbell
• porteiro eletrônico = electronic entry/intercom system
• portaria = concierge/guard desk/front gate area

They refer to different things:

• portaria = the front desk, concierge area, gatehouse, or doorman/guard station
• portão = the gate

So:

• a moça da portaria = the woman who works at the front desk / gatehouse / concierge area
• abrir o portão = open the gate

A simple way to remember it:

• portaria = the place/person managing access
• portão = the physical gate itself

Moça literally means young woman or girl, but in Brazilian Portuguese it is also often used in an everyday, informal, and sometimes polite way to refer to a woman.

So a moça da portaria sounds like:

• the woman at the front desk
• the girl at the concierge desk

Depending on context, it may or may not imply youth strongly. In many cases it just sounds colloquial and natural.

Other possibilities:

• a funcionária da portaria = the employee at the front desk
• a atendente da portaria = the attendant at the front desk
• a porteira = female doorkeeper/porter, though this can sound less common depending on context

So moça is natural in everyday speech, but it is a bit more informal and less job-title-like.

Because de + a contracts to da in Portuguese.

So:

• de + a portaria → da portaria

This is extremely common and mandatory in normal Portuguese.

Other common contractions:

• de + o → do
• em + a → na
• em + o → no
• a + a → à

So a moça da portaria literally means the woman of/from the front desk, which in natural English becomes the woman at the front desk.

Portuguese uses definite articles more often than English does.

In English, you might say:

• If intercom rings, front desk woman can open gate — but this sounds unnatural in English, so you add articles too.

In Portuguese, articles are very normal with nouns, especially specific things in a known setting:

• o interfone = the intercom
• a moça = the woman
• a portaria = the front desk / concierge area
• o portão = the gate

Even where English might omit an article, Portuguese often keeps one. This is something learners just get used to over time.

It can suggest ability, permission, or possibility, depending on context.

• a moça da portaria pode abrir o portão

This could mean:

• she can open the gate because she is able to
• she may open the gate because she is allowed to
• she can open it as the next step in the process

In this kind of building-access context, English usually translates it as can open, and the nuance is often a mix of ability and authorization.

If the sentence wanted to express stronger certainty, Portuguese might say:

• abre o portão = opens the gate
• vai abrir o portão = will open the gate

So pode abrir is softer and more general.

Yes, depending on context.

Because the first clause is future-oriented, English may sometimes naturally say:

• If the intercom rings, the woman at the front desk will be able to open the gate.

That can sound slightly more explicit about the future result.

But a simple present translation is also very natural in English:

• If the intercom rings, the woman at the front desk can open the gate.

Portuguese pode abrir does not force one single English choice. The best translation depends on the situation.

Yes. Portuguese allows some flexibility.

The original:

• Se o interfone tocar, a moça da portaria pode abrir o portão.

You could also say:

• A moça da portaria pode abrir o portão se o interfone tocar.

This means the same thing: The woman at the front desk can open the gate if the intercom rings.

Putting the se clause first often sounds slightly more natural when setting up the condition first, but both are correct.

Yes, very common.

Abrir means to open, and portão is a gate, usually a large entrance gate for a building, house, garage, or condominium.

So abrir o portão is exactly what Brazilians commonly say for:

• opening the front gate
• buzzing someone in
• unlocking and opening access

In apartment-building contexts, this is a very everyday phrase.

In Brazilian Portuguese, portão has a nasal ending because of ão.

A rough guide:

• por sounds like por with a Portuguese r
• tão has a nasal sound, something like towng without fully pronouncing the ng

Very roughly for an English speaker:

• por-TAWN with a nasalized final syllable

Important point:

• ão is one of the most recognizable nasal endings in Portuguese
• it does not sound like a plain English ow

You will hear this ending in many common words:

• não
• mão
• coração
• portão

It sounds like a very typical Brazilian apartment-building or gated-entry situation.

A visitor arrives and uses the building intercom. If it rings, the employee at the building entrance or concierge desk can open the main gate remotely.

This kind of sentence reflects common Brazilian urban life, especially in:

• apartment buildings
• condominiums
• office buildings
• gated residences

So besides being grammatically useful, it is also a very practical everyday sentence.