La jaqueta de la mare és més cara que la camisa de la meva germana.

Catalan usually expresses possession with de + noun:

• la jaqueta de la mare = the mother's jacket
• la camisa de la meva germana = my sister's shirt

So instead of using an English-style 's, Catalan normally uses this de structure.

Because mare is a countable noun and here it is definite, so it normally takes the article la.

• de la mare = of the mother / of mom
• de la germana = of the sister

Catalan uses articles more often than English does. English might say mom's jacket, but Catalan naturally says la jaqueta de la mare.

In standard Catalan, possessives like meu, meva, teu, seva, nostre usually appear with a definite article:

• la meva germana = my sister
• el meu germà = my brother
• la seva casa = his/her house

This is one of the big differences from English. English says my sister, but Catalan normally says the my sister literally, even though that is not how we translate it.

There are some special shorter forms like ma germana or mon pare, but those are more limited by dialect, style, or fixed usage. For a learner, la meva germana is the safe standard pattern.

Because the possessive has to agree with the noun it modifies.

germana is feminine singular, so the possessive must also be feminine singular:

• el meu germà = masculine singular
• la meva germana = feminine singular
• els meus germans = masculine plural
• les meves germanes = feminine plural

So meva matches germana.

Because cara describes la jaqueta, and jaqueta is feminine singular.

In Catalan, adjectives usually agree with the noun they describe:

• un llibre car = an expensive book
• una jaqueta cara = an expensive jacket

In this sentence, the thing being described as more expensive is la jaqueta, so the adjective must be feminine singular: cara.

més ... que is the normal comparative pattern meaning more ... than.

So:

• més cara que = more expensive than
• més gran que = bigger than
• més ràpid que = faster than

The structure is:

[thing 1] + és + més + adjective + que + [thing 2]

So here:

• La jaqueta de la mare és més cara que la camisa de la meva germana.

This is exactly the same basic logic as English X is more expensive than Y.

Here que means than, because it is part of a comparison:

• més cara que = more expensive than

Catalan que can have different meanings depending on context, including that in other sentences. But in comparative structures after més or menys, it means than.

Because és comes from ser, which is used for inherent or identifying qualities, including things like price, size, nationality, and general characteristics.

Being expensive is treated as a characteristic of the jacket here, so Catalan uses ser:

• La jaqueta és cara. = The jacket is expensive.

estar is more often used for states or conditions:

• La porta està oberta. = The door is open.
• Estic cansat. = I am tired.

So és més cara is the natural choice.

Because Catalan only contracts certain combinations.

Common contractions are:

• de + el = del
• a + el = al

But with la, there is no contraction:

• de la mare stays de la mare
• not dla mare

So the sentence correctly keeps de la in both places.

Yes. Catalan often allows ellipsis if the meaning is clear.

For example, if the comparison were between two jackets, you could say:

• La jaqueta de la mare és més cara que la de la meva germana.

Here la stands for la jaqueta.

But in your sentence, the comparison is between a jacket and a shirt, so keeping la camisa makes the meaning fully clear.

Yes, absolutely.

• la jaqueta de la mare can mean the mother's jacket or mom's jacket, depending on context
• la jaqueta de la meva mare explicitly means my mother's jacket

So if you want to make the relationship clearer, de la meva mare is perfectly natural. The shorter de la mare works when the context already makes it clear whose mother is being talked about.

The given word order is the most neutral and natural one:

• La jaqueta de la mare és més cara que la camisa de la meva germana.

Catalan can sometimes move elements around for emphasis, but for ordinary statements, this order is the standard pattern:

subject + verb + comparative + que + second item

So for learners, this is the best model to follow.