Antes de conduzir, aperta o cinto de segurança.

Because antes de is commonly followed by an infinitive in Portuguese when you mean before doing something.

So:

• antes de conduzir = before driving
• antes de sair = before leaving
• antes de comer = before eating

This is a very common pattern in both European and Brazilian Portuguese.

Yes, dirigir can also mean to drive, but in Portugal, conduzir is especially common for driving a vehicle.

So in European Portuguese:

• conduzir = to drive
• dirigir = can also mean to drive, but often also means to direct, to manage, or to address

A learner of Portuguese from Portugal should definitely be comfortable with conduzir for driving.

Aperta is the affirmative imperative for tu from the verb apertar.

• tu apertas = you fasten / you tighten
• aperta! = fasten! / tighten!

In Portuguese, the tu imperative often looks like the tu present form without the final -s:

• tu falas → fala!
• tu comes → come!
• tu abres → abre!
• tu apertas → aperta!

So aperta o cinto de segurança means fasten your seat belt when speaking informally to one person.

Because Portuguese often leaves subject pronouns out when they are understood from the verb form.

Here, aperta already tells you the sentence is addressing tu. So:

• Antes de conduzir, aperta o cinto de segurança.
• Antes de conduzir, tu aperta o cinto de segurança. ❌ not natural

The version without tu is the normal one.

Yes — literally, apertar often means to tighten, to squeeze, or to press. But with cinto de segurança, it is commonly used in the sense of fastening / buckling up.

So:

• apertar o cinto de segurança = to fasten / tighten the seat belt

This is a natural expression in Portuguese. English uses fasten or put on more often, while Portuguese can use apertar idiomatically here.

Portuguese often uses the definite article where English might use a or no article at all.

Here, o cinto de segurança means the seat belt, but in natural English we usually translate it as your seat belt or simply the seat belt, depending on context.

So this is normal Portuguese usage, not something to translate word-for-word.

Literally:

• cinto = belt
• de segurança = of safety / safety

So cinto de segurança is the fixed expression for seat belt.

It is best learned as one whole phrase.

The comma separates the introductory phrase from the main instruction:

• Antes de conduzir, = before driving
• aperta o cinto de segurança. = fasten the seat belt

This comma is natural and helps readability. It works much like English:

• Before driving, fasten your seat belt.

It is informal singular, because aperta is the command form for tu.

If you wanted a more formal or more neutral version, you would usually say:

• Antes de conduzir, aperte o cinto de segurança.

That uses the você / o senhor / a senhora command form.

So:

• aperta = informal, one person
• aperte = formal/neutral, one person

In Portugal, both matter because the choice depends on how you address the person.

If you are speaking to several people informally:

• Antes de conduzir, apertem o cinto de segurança.

If you are being more formal with several people:

• Antes de conduzir, apertem o cinto de segurança.

In this case, the plural imperative is the same form for both vocês and the usual plural command, so the sentence stays apertem.

Usually, learners should stick with antes de + infinitive:

• Antes de conduzir

Portuguese does have a personal infinitive, so forms like conduzires exist. However, in a simple sentence like this, antes de conduzir is the most straightforward and natural choice to learn first.

So for practical purposes, use:

• antes de conduzir = before driving

A simple approximation is:

AN-tesh d’ con-doo-ZEER, uh-PER-tuh oo SEEN-too d’ seg-oo-RAN-suh

A few European Portuguese notes:

• antes often sounds like antesh
• de is often reduced
• unstressed vowels are reduced a lot in European Portuguese
• segurança has stress on ran

A more Portuguese-looking pronunciation guide would be roughly:

[ˈɐ̃t(ɨ)ʃ dɨ kõduˈziɾ, ɐˈpɛɾtɐ u ˈsĩtu dɨ sɨɡuˈɾɐ̃sɐ]

You do not need to memorize the IPA, but it helps to know that European Portuguese often sounds more reduced than learners expect.

Yes. Even though it is a direct command, it can also express a general instruction or safety rule.

So it can mean:

• Before driving, fasten your seat belt.
• Whenever you drive, fasten your seat belt first.

Context decides whether it is a one-time instruction or a general rule.