La hebilla del cinturón se ha roto y tengo que cambiarla.

Because hebilla is a feminine noun, so it takes la.

• la hebilla = the buckle

But cinturón is a masculine noun, so with de + el it becomes del:

• del cinturón = of the belt

So the whole phrase is literally:

• la hebilla del cinturón = the buckle of the belt

Del is a contraction of de + el.

• de = of / from
• el = the
• de + el = del

So:

• la hebilla del cinturón = the buckle of the belt

This contraction is mandatory in Spanish when de is followed by the masculine singular article el.

The only common exception is when El is part of a proper name, such as de El Escorial.

Because romperse is often used when something breaks on its own or when the speaker does not mention who caused it.

• se ha roto = it has broken / it has gotten broken
• ha roto usually means has broken something

Compare:

• La hebilla se ha roto. = The buckle has broken.
• Juan ha roto la hebilla. = Juan has broken the buckle.

So the se here makes it a very natural way to say that the buckle broke.

Both are possible, but they focus on slightly different things.

• se ha roto focuses on the event: it has broken
• está rota focuses on the resulting state: it is broken

So:

• La hebilla se ha roto = the buckle broke / has broken
• La hebilla está rota = the buckle is broken

In this sentence, the speaker is talking about what has happened and then what they need to do next, so se ha roto fits very naturally.

Because romper has an irregular past participle.

• infinitive: romper
• regular-looking form would be rompido — but that is not used here
• correct past participle: roto

So:

• se ha roto = has broken

This is similar to other irregular participles:

• hacer → hecho
• ver → visto
• escribir → escrito

This is a very common question, especially for learners of Spanish from Spain.

In Spain, the present perfect (ha roto) is often used for something that happened recently or is still connected to the present moment.

So:

• La hebilla se ha roto sounds like: the buckle has broken, and that matters now
• La hebilla se rompió simply reports a past event: the buckle broke

Because the sentence continues with y tengo que cambiarla, the result is important right now, so se ha roto is very natural in Spain.

In much of Latin America, people would often use the preterite instead:

• La hebilla del cinturón se rompió y tengo que cambiarla.

Both are correct, but se ha roto is especially typical in Spain.

Yes. Tener que + infinitive is one of the most common ways to say have to in Spanish.

• tengo que cambiarla = I have to change it

Structure:

• tener (conjugated)
• que
• infinitive

Examples:

• Tengo que estudiar. = I have to study.
• Tenemos que salir. = We have to leave.

It is very natural and everyday Spanish.

The la is a direct object pronoun meaning it, and it refers to la hebilla.

Since hebilla is feminine singular, the pronoun is:

• la = it / her for a feminine singular direct object

So:

• cambiarla = to change it

This literally breaks down as:

• cambiar = to change
• la = it

Here, la clearly refers to the buckle, not the belt.

In Spanish, object pronouns can be attached to an infinitive.

So these are both possible:

• tengo que cambiarla
• la tengo que cambiar

Both mean the same thing: I have to change it.

Spanish allows pronouns to be:

1. attached to the infinitive
2. placed before the conjugated verb

In this sentence, cambiarla is perfectly natural.

In this sentence, it refers to la hebilla.

That is because:

• hebilla is feminine: la
• cinturón is masculine: it would be lo

So:

• cambiarla = change the buckle
• cambiarlo = change the belt

This is a useful clue when reading Spanish pronouns: gender often tells you what the pronoun refers to.

Here, cambiar is best understood as replace.

In English, change can mean many things, but in Spanish cambiar often covers both:

• to change
• to switch
• to replace

So in this sentence:

• tengo que cambiarla = I have to replace it

That is the natural meaning because a broken buckle would usually need replacing.

Yes, hebilla is the normal standard word for buckle.

So:

• la hebilla del cinturón = the belt buckle

This is the usual word you would learn and use in everyday Spanish.

Because this is the most natural and standard way to express possession or association in Spanish.

Spanish often uses:

• noun + de + noun

So instead of putting one noun directly before another as English often does, Spanish says:

• la hebilla del cinturón = literally the buckle of the belt

This is much more natural in Spanish than trying to imitate the English pattern belt buckle.

Yes. A few natural alternatives are:

• La hebilla del cinturón está rota y tengo que cambiarla.
• Se ha roto la hebilla del cinturón y tengo que cambiarla.
• La hebilla del cinturón se rompió y tengo que cambiarla.

These are all understandable and natural, but they differ a little:

• se ha roto = very natural in Spain for something recent and relevant now
• está rota = focuses on the current broken condition
• se rompió = simple past, also correct, especially common in many Latin American varieties

Yes: se ha roto is especially characteristic of Spanish from Spain when talking about a recent event that still matters now.

A speaker from Spain might naturally say:

• Se ha roto.

Where many Latin American speakers might prefer:

• Se rompió.

So if you are learning Spanish from Spain, this sentence is a very good model of natural usage.