Si les estovalles són netes, la meva mare hi posa els plats i els gots abans de sopar.

Because adjectives in Catalan agree with the noun they describe.

Here, estovalles is feminine plural, so the adjective must also be feminine plural:

• net = masculine singular
• neta = feminine singular
• nets = masculine plural
• netes = feminine plural

That is why the sentence has les estovalles són netes.

Són is the plural of ser, and it is grammatical here.

In Catalan, ser and estar do not always match English to be in a simple one-to-one way. With net, both can appear, but the nuance can change:

• són netes = describes them as clean
• estan netes = often emphasizes their current state, as in they have been cleaned and are now clean

So the given sentence is correct. In everyday speech, many speakers might also say estan netes in this kind of context.

Catalan normally uses the definite article with possessives before many family words:

• la meva mare
• el meu pare
• la seva germana

That is more natural than leaving the article out. English does not do this, but Catalan usually does.

The article is often omitted in direct address or some fixed expressions, but in a normal sentence la meva mare is the standard form.

Hi is a locative clitic. It usually means something like there, on it, in it, or to that place, depending on context.

In this sentence, hi refers to the place where the plates and glasses are put, understood from the context. So hi posa els plats i els gots means roughly:

• she puts the plates and glasses there
• she puts the plates and glasses on it/on them

It avoids repeating the place explicitly.

Because clitic pronouns normally go before a conjugated verb in Catalan.

So you get:

• hi posa = she puts there/on it

But with an infinitive, gerund, or affirmative imperative, the clitic is attached after the verb:

• posar-hi = to put there/on it
• posant-hi = putting there/on it
• posa-hi! = put it there!

So hi posa is exactly where hi should be in this sentence.

Because in Catalan it is very normal to give each noun its own article in a list or coordination:

• els plats i els gots
• la mare i el pare

English often uses just one the for both nouns, but Catalan commonly repeats the article. That repeated article sounds natural and standard here.

Formally, sopar can be both:

• a noun: dinner/supper
• an infinitive verb: to have dinner / to eat supper

After abans de, Catalan very often uses an infinitive, so here abans de sopar is most naturally understood as before having dinner.

In English, though, it is often translated more simply as before dinner.

Because this structure is behaving like abans de + infinitive:

• abans de sortir = before leaving
• abans de menjar = before eating
• abans de sopar = before having dinner

So Catalan is not using the dinner here. It is using the verb form sopar, which is why no article appears.

They are different words:

• si without an accent = if
• sí with an accent = yes

So at the start of this sentence, Si les estovalles són netes... means If the tablecloths are clean..., not Yes the tablecloths are clean...