La malnova fenestro povas rompiĝi pro la vento.

In Esperanto, mal- is a very common prefix that gives the opposite meaning of a word.

• nova = new
• malnova = old

So instead of learning a completely separate word for old, you can often build it from its opposite. This is a very typical Esperanto pattern.

Also, malnova ends in -a because it is an adjective, and adjectives in Esperanto always end in -a.

All Esperanto nouns end in -o.

So:

• fenestro = window

This makes it easy to recognize parts of speech. In this sentence, fenestro is the noun being described by la malnova.

Adjectives in Esperanto must match the noun they describe in number and case.

Here:

• fenestro is singular
• it is not accusative
• so the adjective stays in its basic form: malnova

If the noun were plural, you would get:

• la malnovaj fenestroj = the old windows

If it were accusative, you would add -n to both the noun and the adjective.

Povas is the present-tense form of povi, which means to be able to or can.

• mi povas = I can
• ĝi povas = it can

In this sentence, la malnova fenestro povas rompiĝi means the old window can break or the old window may get broken.

The ending -as marks the present tense.

This is one of the most important points in the sentence.

• rompi usually means to break something
• rompiĝi means to break / to become broken

So:

• Mi rompas la fenestron. = I break the window.
• La fenestro rompiĝas. = The window breaks / gets broken.

In your sentence, the window is not breaking something else. The window itself is undergoing the change. That is why Esperanto uses rompiĝi.

The suffix -iĝ- often means to become, to get into a state, or to happen to itself.

So:

• rompi = to break something
• rompiĝi = to become broken

This suffix often turns a verb into something more intransitive.

A few similar patterns:

• fermi = to close something

• fermiĝi = to close, to become closed

• varmigi = to make something warm
• varmiĝi = to become warm

So rompiĝi is very natural here because the sentence talks about the window ending up broken, not about someone actively breaking it.

Because fenestro is the subject of the sentence, not the direct object.

In Esperanto, the accusative ending -n usually marks the direct object.

Here:

• La malnova fenestro = the subject
• povas rompiĝi = can break / can become broken

The window is the thing that breaks, so it is the subject.

Compare:

• La vento rompas la fenestron. = The wind breaks the window.

There, fenestron has -n because it is the direct object of rompas.

Pro means because of, due to, or on account of.

So:

• pro la vento = because of the wind / due to the wind

It gives the cause or reason.

In this sentence, it means the wind is the reason the window might break.

These little words are similar, but not the same.

• pro = because of, due to
• per = by means of, using
• de = from, of, by (in some passive-like contexts)

Here, the idea is cause, so pro fits best.

• rompiĝi pro la vento = break because of the wind

If you used per, it would sound more like the wind is a tool or means, which is less natural here.

If you used de, that would not be the normal way to express this idea in such a sentence.

La is the definite article, meaning the.

In pro la vento, it refers to a specific wind or to the wind in the situation being discussed. Very often Esperanto uses la in places where English also would.

You might also see pro vento in some contexts, but pro la vento is more natural if you mean a particular wind that is causing the problem.

Yes, depending on context.

Povas basically means can / is able to / may possibly. So in English, this sentence could be translated in more than one natural way:

• The old window can break because of the wind.
• The old window may break because of the wind.
• The old window could break because of the wind.

The exact best translation depends on what nuance the context gives.

Not completely. Esperanto word order is fairly flexible, because endings help show grammatical roles.

The normal order here is:

• La malnova fenestro povas rompiĝi pro la vento.

But other orders are possible, especially for emphasis, such as:

• Pro la vento la malnova fenestro povas rompiĝi.

That puts more attention on the cause.

Even though word order can move around, the most neutral and beginner-friendly pattern is usually:

subject + verb + other elements

That would be:

La vento povas rompi la malnovan fenestron.

Notice the difference:

• La malnova fenestro povas rompiĝi pro la vento.
  The old window can break / get broken because of the wind.

• La vento povas rompi la malnovan fenestron.
  The wind can break the old window.

In the second sentence:

• rompi is transitive
• fenestron gets -n because it is the direct object
• malnovan also gets -n to match fenestron