Learn Hardcore Portuguese (Portugal): Se a campainha tocar, abre a porta com calma. - If the doorbell rings, open the door calmly.

It’s the future subjunctive. Portuguese uses the future subjunctive after se to talk about a possible future event: Se a campainha tocar. For many verbs the 3rd person singular of the future subjunctive looks identical to the infinitive (here, tocar).

Why not toque (present subjunctive) after se?

With conditional se meaning if about a future possibility, Portuguese requires the future subjunctive, not the present subjunctive. So you say Se a campainha tocar, not Se a campainha toque. You would use toque in other structures, e.g., Mesmo que a campainha toque (even if the bell rings).

Is abre an imperative?

Yes. Abre is the affirmative imperative for tu (informal singular). In European Portuguese, the tu affirmative imperative is the present indicative form without the final -s: tu abres → abre.

When would I use abra instead of abre?

Abra is the imperative for você / o senhor / a senhora (politer or more formal address).
Examples:
- Informal: Se a campainha tocar, abre a porta com calma.
- Polite/formal: Se a campainha tocar, abra a porta com calma.

How do I make it negative (Don’t open the door)?

Use the present subjunctive for negative commands:

Informal (tu): Não abras a porta.
Polite/formal (você): Não abra a porta.

What about talking to more than one person?

Use the plural imperative (present subjunctive for vocês):

Se a campainha tocar, abram a porta com calma.
Negative: Não abram a porta.

Why is there a comma after the se-clause?

When the conditional clause comes first, Portuguese normally writes a comma: Se a campainha tocar, ... If you invert the order, the comma is usually unnecessary: Abre a porta com calma se a campainha tocar.

Can I change the word order to Se tocar a campainha?

Yes. Both Se a campainha tocar and Se tocar a campainha are fine. The latter places the subject after the verb and can sound a bit more formal or stylistic, but both are common.

Could I use quando instead of se?

Se = if (it may or may not happen).
Quando = when (you assume it will happen). So Quando a campainha tocar, abre a porta com calma implies certainty; Se a campainha tocar... leaves it conditional.

Why com calma and not an adverb like calmamente or the adjective calmo?

Com calma is a very natural, everyday adverbial phrase meaning “calmly/without rushing.”
Calmamente exists but sounds more formal or bookish.
Calmo is an adjective and would describe a noun (e.g., a calm person), not how you open the door.

What does tocar mean here? I thought it meant “to play (an instrument)” or “to touch.”

Tocar is versatile:

tocar a campainha = to ring the doorbell (someone does the ringing).
a campainha tocar = the bell rings (the bell is the subject).
It also means “to play” (an instrument) and “to touch” (often with em/na: tocar em).

Can I say Se tocar à campainha, ...?

Yes, that’s common and means “if someone rings the doorbell,” with an implicit subject. More explicit options:

Se alguém tocar à campainha, ...
If you want the bell as the subject, keep your original: Se a campainha tocar, ... Note the preposition in tocar à campainha (ring at the bell).

Why is it abre a porta (with a) and not abre à porta?

Here a is the definite article before porta (the door). À is a contraction of the preposition a + article a and is used in expressions like tocar à campainha. There is no preposition before porta in abrir a porta, so you just use the article a.

How do I say “open it” with a pronoun?

In European Portuguese, affirmative imperatives take enclisis (pronoun after the verb, with a hyphen):

Abre-a com calma. (Open it — referring to a porta)
Polite/formal: Abra-a com calma. For the negative, use proclisis:
Não a abras.
Não a abra. Indirect objects also go after the verb in affirmative imperatives: Abre-lhe a porta (open the door for him/her).

What if I want a more tentative or hypothetical tone?

Use the imperfect subjunctive in the se-clause and a conditional (or imperfect indicative in European Portuguese speech) in the main clause:

Se a campainha tocasse, abrias a porta com calma? (If the bell happened to ring, would you open the door calmly?)

How do I pronounce campainha and the nh sound?

nh = a palatal nasal, like the ny in English “canyon.”
campainha roughly: kahm-pah-EEN-yah (in European Portuguese many vowels reduce, but the key is the -nh- sounding like “ny”).
abre = AH-breh; porta = POR-tah (the single r is a tap/flap in most European accents).