Abra a boca, por favor.

Abra comes from the verb abrir, meaning to open.

In Abra a boca, por favor, abra is the imperative form used with você. In Brazilian Portuguese, commands for você usually use the same form as the present subjunctive:

• abrir → que você abra
• command: Abra!

So this sentence is giving a command or instruction to one person in the você form.

This is one of the most common questions learners have.

In Brazilian Portuguese, the command form depends on which you is being used:

• você → abra
• tu → abre

So:

• Abra a boca. = command to você
• Abre a boca. = command to tu

Because Brazilian Portuguese very often uses você, abra is a very common form in instructions, service situations, and polite commands.

The hidden subject is usually você.

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

• Abra a boca, por favor. literally corresponds to:
• Você, abra a boca, por favor.

But saying você explicitly is usually unnecessary unless you want emphasis.

Portuguese often uses the definite article with body parts where English uses my, your, his, and so on.

So Portuguese commonly says:

• abra a boca = literally open the mouth

But the meaning is naturally understood as open your mouth.

This pattern is very normal in Portuguese, especially when the owner is obvious from context.

Examples:

• Feche os olhos. = Close your eyes.
• Levante a mão. = Raise your hand.

Yes, you can, but it is usually less natural in this kind of situation.

Abra a boca is the standard, natural way.

Abra sua boca may sound:

• more emphatic,
• more contrastive,
• or less idiomatic in everyday speech.

For example, sua might be used if you are contrasting with someone else’s mouth, or if you really want to emphasize ownership. In normal instructions, especially from a doctor or dentist, Abra a boca is what you would usually hear.

By itself, the imperative can sound direct, because it is a command. But in context, Abra a boca is very normal and not rude when giving practical instructions, especially in places like:

• a doctor’s office,
• a dentist’s office,
• a parent speaking to a child,
• a teacher guiding a student.

Adding por favor makes it more polite:

• Abra a boca, por favor.

So in a medical setting, this sounds completely natural and polite.

Por favor is flexible. These are all possible:

• Abra a boca, por favor.
• Por favor, abra a boca.
• Abra, por favor, a boca.

The first two are the most common and natural.

In everyday Brazilian Portuguese, Abra a boca, por favor and Por favor, abra a boca are both excellent choices.

A careful pronunciation is roughly:

AH-brah ah BOH-kah, por fah-VOR

A more IPA-style version in Brazilian Portuguese would be approximately:

/ˈabɾɐ a ˈbokɐ poɾ faˈvoɾ/

A few notes:

• r in abra is the tapped r, similar to the quick sound in the American English pronunciation of butter for many speakers.
• boca has stress on the first syllable: BO-ca.
• favor has stress on the second syllable: fa-VOR.
• In connected speech, abra a may sound a bit smoother and less separated than learners expect.

Yes, a Brazilian would absolutely say this.

It is natural in the right context, especially when someone is being instructed to physically open their mouth.

That said, another very common polite alternative is:

• Pode abrir a boca, por favor? = Can you open your mouth, please?

This sounds a little softer because it is framed as a question rather than a direct command.

So both are natural:

• Abra a boca, por favor. = direct but polite
• Pode abrir a boca, por favor? = softer and very common

If you are speaking to multiple people using vocês, the command becomes:

• Abram a boca, por favor.

So:

• one person: Abra a boca, por favor.
• more than one person: Abram a boca, por favor.

This is the normal plural form in Brazilian Portuguese.

With tu, the command would normally be:

• Abre a boca, por favor.

So compare:

• você → Abra a boca
• tu → Abre a boca

In Brazil, usage of tu varies a lot by region. In many parts of Brazil, você is much more common, which is one reason learners often see abra.

It can be both, depending on context.

Literally:

• Abra a boca. = Open your mouth.

Figuratively, abrir a boca can also mean something like:

• to start talking,
• to speak up,
• sometimes even to reveal something.

But in this sentence, especially with por favor, the most likely meaning is the literal one.

The negative command is:

• Não abra a boca.

This means Don’t open your mouth.

In Portuguese, negative commands use the subjunctive-based form as well, so não abra is correct for você.

For comparison:

• positive: Abra a boca.
• negative: Não abra a boca.

An exclamation mark is possible, but it is not required.

Both of these are correct:

• Abra a boca, por favor.
• Abra a boca, por favor!

Without the exclamation mark, the sentence can look calmer and more neutral. With it, it may feel more forceful or expressive. In many real-life written contexts, especially in teaching materials, punctuation is chosen based on tone rather than grammar.