Learn Hardcore Portuguese (Brazil): A sala fica clara quando a janela está aberta. - The living room becomes bright when the window is open.

A sala é clara.
The room is bright (as a general, inherent characteristic).
A sala está clara.
The room is bright (right now, in this current state).
A sala fica clara quando a janela está aberta.
The room gets / becomes bright when the window is open (whenever this condition happens).

So ficar often means:

to become / to get (change of state):
- Ele fica nervoso. = He gets nervous.
- Fica escuro às 6 horas. = It gets dark at 6 o’clock.
to end up somewhere or in some state:
- Fiquei em casa. = I stayed / ended up staying at home.

Here it emphasizes the change of state that happens because the window is open.

What tense is fica here? Does it mean "will become" like a future?

Fica is present tense, indicative mood: ele/ela fica.

In Portuguese, the present tense is very often used for:

General truths or facts
A água ferve a 100 graus. = Water boils at 100 degrees.
Habits or repeated actions
Eu estudo à noite. = I study at night.

In A sala fica clara quando a janela está aberta, both fica and está are in the present indicative, expressing a general, repeated situation:

Whenever the window is open, the room gets bright.

You could translate it as:

The room gets bright when the window is open.
or The room becomes bright whenever the window is open.

It is not a grammatical future, even if in English you might sometimes say:

The room will get bright when the window is open.

Why is it clara and not claro?

In Portuguese, adjectives agree in gender and number with the noun they describe.

sala is a feminine singular noun → a sala
therefore the adjective must also be feminine singular → clara

Pattern:

o quarto é claro. (masculine singular: claro)
a sala é clara. (feminine singular: clara)
os quartos são claros. (masculine plural: claros)
as salas são claras. (feminine plural: claras)

So you use clara simply because sala is feminine.

What exactly does clara mean here? "Clear" or "bright"?

In this context, clara means "bright / well-lit", not "clear" in the sense of "easy to understand".

Common meanings of claro/clara:

Light-colored
- Olhos claros. = Light-colored eyes.
Bright / well lit
- Um quarto claro. = A bright room.
Clear / obvious (often in spoken reactions)
- Claro! = Of course! / Sure!
- Está claro? = Is it clear?

Here, for a sala fica clara, it is talking about light, so the natural translation is "The room gets bright" or "The room becomes bright".

Why does the sentence use quando a janela está aberta and not some subjunctive form like quando a janela estiver aberta?

Both structures exist, but they are used in different situations.

quando + present indicative (quando a janela está aberta)
Used for general truths, habits, or repeated situations:
- A sala fica clara quando a janela está aberta.
  Whenever the window is open (in general), the room gets bright.
quando + future subjunctive (quando a janela estiver aberta)
Used for a specific future event that has not happened yet:
- Quando a janela estiver aberta, você vai sentir um vento forte.
  When the window is open (in the future), you will feel a strong wind.

In your sentence, we are describing a general rule, so the simple present está is correct and natural.

Why is it está aberta and not é aberta?

The difference is between a temporary state (using estar) and a more permanent or characteristic fact / passive meaning (using ser).

A janela está aberta.
The window is open (right now; this is its current state).
A janela é aberta.
Depending on context, this sounds more like a passive voice:
- The window is opened (by someone, as a general or habitual action).
  Or like a general characteristic (but it is rare and often sounds odd).

In everyday speech, to say that something is in an open state right now, you almost always use estar + aberta:

A porta está aberta. = The door is open.
As lojas estão abertas. = The stores are open.

So quando a janela está aberta is the natural way to say "when the window is open" (state), not "is opened" (action).

Why is it aberta (with -a) and not aberto?

Again, this is agreement in gender and number.

janela is feminine singular → a janela
the participle/adjective must match: aberta (feminine singular)

Compare:

o livro está aberto. = the book is open (masculine singular)
a porta está aberta. = the door is open (feminine singular)
os livros estão abertos. = the books are open (masculine plural)
as janelas estão abertas. = the windows are open (feminine plural)

So aberta agrees with a janela.

Could we change the order to Quando a janela está aberta, a sala fica clara?

Yes, absolutely. Both orders are correct and natural:

A sala fica clara quando a janela está aberta.
Quando a janela está aberta, a sala fica clara.

Portuguese allows this kind of flexibility. Placing quando a janela está aberta at the beginning can slightly emphasize the condition, but the meaning is the same.

Just remember to use a comma when the quando-clause comes first:

Quando a janela está aberta, a sala fica clara.

Could I say A sala é clara quando a janela está aberta? Is it wrong?

It is grammatically correct, but the nuance changes.

A sala fica clara quando a janela está aberta.
Focus on the change: it becomes / gets bright under that condition.
A sala é clara quando a janela está aberta.
Sounds more like: Under the condition that the window is open, you can describe the room as bright.
It focuses more on classifying the room (using ser) in that situation, less on the idea of becoming bright.

In everyday speech, for this kind of cause-effect relationship (window opens → room gets bright), fica is more natural.

Another very natural alternative is:

A sala fica clara com a janela aberta.
(Literally: The room gets bright with the window open.)

Why do we say a sala and a janela with the article a? Could we drop it?

Here, a is the definite article: "the".

a sala = the room (feminine)
a janela = the window (feminine)

In this kind of sentence, when you are talking about a specific room and its window (for example, in a house you both know), you normally use the definite article.

You cannot drop the article here in standard Portuguese:

❌ Sala fica clara quando janela está aberta. (incorrect)
✅ A sala fica clara quando a janela está aberta.

You could change the meaning by switching to the indefinite article:

Uma sala fica clara quando uma janela está aberta.
A room gets bright when a window is open (more generic).

But that is not the same sentence; it sounds more like a general statement about any room and any window.

What is the difference between quando and se here? Could I say Se a janela está aberta?

Both quando and se introduce clauses, but they are not interchangeable here.

quando = when (time condition)
se = if (condition, possibility)

In your sentence:

Quando a janela está aberta, a sala fica clara.
Whenever / when the window is open, the room gets bright.
This is a time-based, regular situation.

If you said:

Se a janela está aberta, a sala fica clara.

it would sound unusual. More natural would be:

Se a janela estiver aberta, a sala fica clara.
If the window is open, the room gets bright.

This shifts the focus to a conditional possibility, not a normal, repeated pattern.

So:

Use quando for "when(ever) this happens..." (time).
Use se for "if this happens..." (condition/possibility).

Why sala and not quarto or another word for "room"?

Portuguese has several words that can all be translated as "room", but they are used differently:

a sala – usually living room or common room
- sala de estar = living room
- sala de aula = classroom
o quarto – bedroom
- quarto de casal = double bedroom
- quarto de solteiro = single bedroom
a sala on its own most commonly suggests a living room in a house.

So A sala fica clara quando a janela está aberta is more like:

The living room gets bright when the window is open.

If you wanted to talk about a bedroom, you’d say:

O quarto fica claro quando a janela está aberta.

How would I say "The room gets dark when the window is closed" using the same structure?

You can mirror the structure almost exactly:

A sala fica escura quando a janela está fechada.

Breakdown:

A sala = the room / living room
fica = gets / becomes
escura = dark (feminine, agreeing with sala)
quando = when
a janela = the window
está fechada = is closed (feminine, agreeing with janela)

Or with quarto:

O quarto fica escuro quando a janela está fechada.
(The bedroom gets dark when the window is closed.)

Any pronunciation tips for this sentence?

Key points for Brazilian Portuguese pronunciation:

sala – SA-la
- s like English s in see
- final a is an open "ah" sound.
fica – FEE-ka
- fi like fee, ca like cah (hard k sound).
clara – KLA-ra
- cl like cl in clap
- r between vowels is a soft flap (similar to the American tt in water when pronounced quickly).
quando – roughly KWAN-doo
- qu
  - a → qua like kwah
- an is nasal: air goes through your nose; don’t pronounce a clear n at the end.
janela – zha-NE-la
- j like the s in measure or French j in jour.
está – es-TAH
- stress on the last syllable -tá.
aberta – a-BER-ta (in many accents, r is a soft flap here)

All vowels should be clearly pronounced; avoid reducing them to a schwa sound like in English unstressed syllables.