Binuksan niya ang bintana dahil mainit sa kwarto.

Filipino very often uses verb-first word order.

So Binuksan niya ang bintana is a normal way to say:

• He/She opened the window

A very literal breakdown is:

• Binuksan = opened
• niya = by him / by her
• ang bintana = the window

This can feel unusual to English speakers because English usually starts with the subject, but in Filipino, starting with the verb is extremely common.

Binuksan comes from the root bukas, meaning open in the sense of opening something.

It is formed with:

• -in- infix
• a verb form that marks completed aspect
• object-focused morphology

So binuksan means opened or was opened depending on context, but in this sentence it is best understood as opened.

A learner-friendly way to think about it is:

• bukas = open
• binuksan = opened

Be careful: bukas can also mean tomorrow in other contexts, but here it is clearly the verb root related to opening.

Because the verb binuksan is in an object-focus form, the doer is marked with the genitive pronoun, not the nominative one.

So:

• niya = he/she as the doer in this kind of sentence
• siya = he/she as the main ang-marked topic/subject-like element

In this sentence:

• Binuksan niya ang bintana
• literally: Opened by him/her the window

That is why niya is correct here.

Ang marks the noun phrase that is being highlighted as the main topic/focus of the clause.

Here, the verb form binuksan is object-focused, so the thing affected by the action is marked by ang:

• ang bintana = the window

That matches the verb choice:

• Binuksan niya ang bintana
• The focused element is the window, the thing that got opened.

So ang bintana is not random; it works together with binuksan.

It can do either, depending on the sentence.

In this sentence, niya means he/she as the doer of the action:

• Binuksan niya ang bintana = He/She opened the window

But in another sentence, niya could mean his/her:

• ang libro niya = his/her book

So the function depends on context.

You do not know from the pronoun alone.

Filipino third-person singular pronouns are generally gender-neutral:

• siya = he/she
• niya = by him/by her, his/her
• kaniya = to him/to her, his/hers

So Binuksan niya ang bintana can mean either:

• He opened the window
• She opened the window

You need context to know which one is intended.

Filipino often does not use a separate verb like is or was in sentences of description.

So:

• mainit = hot
• sa kwarto = in the room

Together:

• mainit sa kwarto = it is hot in the room / it was hot in the room

This is very normal in Filipino. The adjective itself can function as the predicate.

Because kwarto here is not the focused noun of the clause. It is part of a location phrase.

• sa is commonly used for locations:
  • sa kwarto = in the room

So the clause means:

• mainit sa kwarto = it is hot in the room

If you used ang kwarto, that would change the structure and emphasis of the sentence.

Yes, kasi could also be used in many everyday contexts.

• dahil = because
• kasi = because

In general:

• dahil can sound a bit more neutral or slightly more formal
• kasi is very common in casual speech

So these are both natural:

• Binuksan niya ang bintana dahil mainit sa kwarto.
• Binuksan niya ang bintana kasi mainit sa kwarto.

The meaning is basically the same.

It can correspond to either of those natural English translations.

Literally, it is closer to:

• hot in the room

In natural English, that often becomes:

• it is hot in the room
• the room is hot

So both are good ways to understand it.

Yes, that is a good question. Both spellings may be seen, but kuwarto is often preferred in more modern Filipino spelling because it reflects local pronunciation more closely.

So you may encounter:

• kwarto
• kuwarto

Both refer to room.

In everyday writing, many people still use kwarto, so learners should recognize both.

It is better to think in terms of aspect rather than tense.

The verb binuksan shows completed aspect, meaning the opening action is completed.

So in English, it will usually be translated as something like:

• opened
• has opened in some contexts

The second part, mainit sa kwarto, does not itself mark tense clearly. Depending on context, English might say:

• because it is hot in the room
• because it was hot in the room

So Filipino often leaves some time reference to context.

Yes. Filipino is flexible here.

You can say:

• Binuksan niya ang bintana dahil mainit sa kwarto.

You could also put the reason first:

• Dahil mainit sa kwarto, binuksan niya ang bintana.

Both are natural. The second version puts more emphasis on the reason first.

A very literal breakdown would be:

• Binuksan = opened
• niya = by him / by her
• ang bintana = the window
• dahil = because
• mainit = hot
• sa kwarto = in the room

So a very literal rendering is:

• Opened by him/her the window because hot in the room.

That is not good English, of course, but it helps show how Filipino builds the sentence.