La revisió veterinària és demà.

La is the feminine singular definite article, meaning the.

The noun revisió is feminine, so it takes la:

• la revisió = the check-up / the examination

Catalan articles have to agree with the noun in gender and number:

• el = masculine singular
• la = feminine singular
• els = masculine plural
• les = feminine plural

So here, la is there because revisió is a feminine singular noun.

Revisió is a noun meaning something like check-up, inspection, review, or examination, depending on context.

In this sentence, with veterinària, it means a veterinary check-up or vet check-up.

A few useful comparisons:

• revisió mèdica = medical check-up
• revisió del cotxe = car inspection/service
• revisió veterinària = veterinary check-up

So revisió is a fairly general word, and the adjective tells you what kind of check-up it is.

In Catalan, adjectives often come after the noun, much more often than in English.

So:

• revisió veterinària = literally check-up veterinary
• natural English: veterinary check-up

This noun + adjective order is very normal in Catalan:

• cita mèdica = medical appointment
• consulta dental = dental consultation
• assistència tècnica = technical assistance

You usually should not try to copy English adjective order directly into Catalan.

Because the adjective has to agree with the noun it describes.

Here, revisió is feminine singular, so the adjective must also be feminine singular:

• revisió veterinària = feminine singular
• control veterinari = masculine singular

Compare:

• el servei veterinari = the veterinary service
• la revisió veterinària = the veterinary check-up

So veterinària does not mean the patient is female or the vet is female. It just agrees grammatically with revisió.

Catalan uses ser in sentences like this to say when something takes place:

• La revisió veterinària és demà. = The vet check-up is tomorrow.
• La reunió és dilluns. = The meeting is Monday.

Even though English learners often associate ser with permanent things and estar with temporary ones, that is too simplistic. Here, és is used because you are identifying the scheduled time of an event.

So for dates, times, and scheduled events, ser is the normal choice.

Because demà is an adverb meaning tomorrow, and in Catalan it normally appears without a preposition.

So you say:

• és demà = is tomorrow
• arribo demà = I arrive tomorrow
• demà al matí = tomorrow morning

This is similar to English, where you also say tomorrow, not on tomorrow.

Yes, Catalan word order is somewhat flexible, although La revisió veterinària és demà is the most neutral and natural version.

You could also say:

• Demà és la revisió veterinària.

This puts more focus on demà.

But the original sentence is the most straightforward if you are simply stating the schedule.

No, that would usually sound wrong for this meaning.

In la revisió veterinària, veterinària is directly modifying the noun revisió to form one idea: veterinary check-up.

If you say:

• La revisió és veterinària

then veterinària is treated as the predicate after és, as if you were saying The check-up is veterinary, which is unnatural in this context.

So if you mean the veterinary check-up is tomorrow, keep the noun phrase together:

• La revisió veterinària és demà.

The written accents help show stress and sometimes distinguish words.

• revisió → stress on the last syllable: re-vi-SIÓ
• veterinària → stress on -nà-: ve-te-ri-NÀ-ri-a
• és → this is the verb is

The accent in és also helps distinguish it from es, which is a different word used as a pronoun.

So the accents are important both for pronunciation and for correct spelling.