Learn Hardcore Portuguese (Brazil): Por favor, mantenha a janela fechada quando estiver chovendo. - Please keep the window closed when it is raining.

“mantenha” = “keep” (as a request/command) → “Please, keep the window closed…”
“mantém” is the present indicative (he/she/you keep) → “Ele mantém a janela fechada.” (He keeps the window closed.)
“manter” is the infinitive → “manter a janela fechada é importante.” (To keep the window closed is important.)

In instructions, signs, or polite requests, “mantenha” is the standard form addressing the reader directly.

Why is there no subject pronoun like “você” in the sentence?

In Portuguese, the imperative normally omits the subject pronoun. The subject is understood from the verb form:

“Mantenha a janela fechada…” = (Você) mantenha… (You, keep…)

Adding “você” in an imperative like this is usually unnecessary and can sound a bit too strong or emphatic:

“Você mantenha a janela fechada…” → sounds closer to “YOU keep the window closed…”, with emphasis, maybe even slightly scolding.

So leaving out “você” is the natural, polite way.

Why is it “Por favor, mantenha…”? Can “por favor” go in another place?

Yes. “Por favor” can move around in the sentence. All of these are possible:

Por favor, mantenha a janela fechada quando estiver chovendo.
Mantenha, por favor, a janela fechada quando estiver chovendo.
Mantenha a janela fechada, por favor, quando estiver chovendo.

The meaning doesn’t change, only the rhythm or emphasis.

At the beginning, it sets a polite tone from the start (very common in writing and signs).
In the middle or end, it can sound a bit more conversational.

All are polite; the original is the most neutral and typical for written requests.

Why is it “a janela” and not just “janela” without the article?

In Portuguese, singular countable nouns almost always need a definite article (o / a / os / as) when you’re talking about a specific thing:

a janela = the window

Saying just “janela fechada” (without “a”) would usually sound incomplete or like part of a longer phrase, not a full object of the verb. For example:

Mantenha a janela fechada. ✅
Mantenha janela fechada. ❌ (sounds wrong in standard Brazilian Portuguese)

So “a janela” is required because we’re talking about a specific window (e.g., in a room or car).

Why is it “fechada” and not “fechado”?

Portuguese adjectives agree in gender and number with the noun they refer to:

janela is feminine singular → a janela
therefore the adjective/past participle must be feminine singular → fechada

So:

a janela fechada (feminine singular) ✅
o livro fechado (masculine singular) ✅
as janelas fechadas (feminine plural) ✅

“Fechado” would be used with a masculine noun (e.g. o portão fechado – the closed gate).

Is “fechada” here an adjective or part of a verb tense?

Here, “fechada” is functioning as an adjective (or past participle used adjectivally) describing the state of the window:

a janela fechada = the window in a closed state

The structure is basically:

mantenha (keep)
- a janela (the window)
  - fechada (closed)

So it’s not a compound verb tense like “foi fechada” (was closed). It’s just telling you to keep the window in the closed state.

What’s the difference between “mantenha a janela fechada” and “feche a janela”?

They’re related but not the same:

Feche a janela.
- Close the window (now).
- Focuses on the action of closing it at that moment.
Mantenha a janela fechada.
- Keep the window closed.
- Focuses on the ongoing state: don’t let it be opened.

In the full sentence:

Por favor, mantenha a janela fechada quando estiver chovendo.
→ Not only close it once; keep it closed whenever it’s raining.

What tense/mood is “estiver” in “quando estiver chovendo”?

“Estiver” is present subjunctive of “estar”.

It’s used because of the conjunction “quando” referring to a future or uncertain time:

quando estiver chovendo = when it is raining (at that time in the future / whenever that situation happens)

In Portuguese, after “quando” (and similar words like “se”, “enquanto”, etc.) you often use the subjunctive when you talk about a future or hypothetical situation:

Quando você chegar, me ligue.
(When you arrive, call me. – “chegar” is in the subjunctive form chegar = chegar? Wait, correct form is chegar vs chegar? Actually: “quando você chegar” is subjunctive, same spelling as infinitive but different mood.)

So “estiver” here marks that this is a condition in the future / not yet realized.

Why is it “quando estiver chovendo” and not just “quando chove”?

You could grammatically say:

Por favor, mantenha a janela fechada quando chove.

…but it sounds unnatural in Brazilian Portuguese for a general instruction.

Differences:

quando estiver chovendo
- literally: when it is raining
- uses subjunctive + gerund → emphasizes an ongoing situation
- very natural in rules, warnings, instructions
quando chove
- literally: when it rains
- more like a general statement of fact (when it rains, the streets flood)
- used more in descriptive sentences, not so much in this kind of instructional rule.

So “quando estiver chovendo” is the idiomatic choice here.

What does “estiver chovendo” literally mean, and why use “chovendo”?

Literally:

estiver = (subjunctive form of) “to be”
chovendo = raining (the gerund of chover – to rain)

So “estiver chovendo” ≈ “is being raining” in structure, but in natural English we say “is raining”.

Portuguese often uses “estar + gerúndio” (*estar + verb in -ndo) to express *continuous actions:

está chovendo = it is raining
está dormindo = he/she is sleeping

Here, the subjunctive “estiver chovendo” gives: when it *is raining (at that moment in the future)*.

Is this sentence formal, informal, or neutral?

The sentence is polite and neutral.

The verb form “mantenha” is the imperative for você (the standard “you” in Brazilian Portuguese) and also works for o senhor / a senhora (formal “you”).
The use of “Por favor” adds politeness.

This is exactly the style you’d see on:

signs (e.g. in buses, offices, hospitals)
written instructions
polite spoken requests in normal situations

It’s not slangy or overly formal; it’s standard polite register.

Could I say “Por favor, mantenha a janela fechada quando chover” instead?

Yes, that is also correct and natural:

Por favor, mantenha a janela fechada quando chover.

Difference in nuance:

quando chover
- still uses subjunctive (chover)
- more like “when it (ever) rains / whenever it rains”
- sounds a bit more general and slightly more compact.
quando estiver chovendo
- focuses more strongly on the time it is actually raining (ongoing rain).

In practice, both are fine for a sign or instruction. “Quando estiver chovendo” slightly emphasizes the ongoing state of rain.

Why is there a comma after “Por favor”?

“Por favor” here works as a parenthetic/introductory phrase (like “please,” in English at the start of a sentence).

In writing, you usually separate such expressions with a comma:

Por favor, mantenha a janela fechada…
Por favor, não fume aqui.

You could also place “por favor” elsewhere with commas:

Mantenha, por favor, a janela fechada…
Mantenha a janela fechada, por favor, quando estiver chovendo.

So the comma is standard punctuation when “por favor” comes first.

Does “janela” specifically mean a house window, or can it be other kinds of windows?

“Janela” means any kind of window:

window in a house or apartment
janela do carro (car window)
janela do ônibus (bus window)
janela do avião (airplane window)

The sentence itself doesn’t specify the location; context would tell you what window is meant.