El veterinario la va a esterilizar mañana.

La is a direct object pronoun meaning her or it, depending on context.

In this sentence, it most likely refers to a female animal that has already been mentioned, such as a dog or cat. Spanish uses grammatical gender, so la tells you the thing being sterilized is treated as feminine.

For example, if the earlier context was la perra or la gata, then la replaces that noun.

Because in Spanish, object pronouns like me, te, lo, la, nos, los, las usually go before the conjugated verb.

Here, the conjugated verb is va.

So:

• El veterinario la va a esterilizar mañana.

But with a structure like ir a + infinitive, Spanish also allows the pronoun to be attached to the infinitive:

• El veterinario va a esterilizarla mañana.

Both are correct and mean the same thing.

This is the very common Spanish structure ir a + infinitive, which means to be going to + verb.

So:

• va a esterilizar = is going to sterilize / is going to spay

It usually expresses the near future or an intended future action.

In this sentence, it means the veterinarian plans to do it tomorrow.

They come from different parts of the sentence:

• va = from the verb ir
• a esterilizar = the a that belongs to the structure ir a + infinitive

So the pattern is:

• la = direct object pronoun
• va = is going
• a esterilizar = to sterilize

This is completely normal in Spanish, even if it sounds repetitive at first.

Here it means tomorrow.

Mañana can mean either tomorrow or morning, but context tells you which one is intended.

In this sentence:

• mañana = tomorrow

If you wanted in the morning, Spanish would more naturally say something like:

• por la mañana
• mañana por la mañana = tomorrow morning

Because el veterinario means the veterinarian, referring to a specific person.

Spanish often uses the article when talking about a specific noun:

• el veterinario = the vet / the veterinarian

But after ser, professions often appear without the article:

• Es veterinario. = He is a veterinarian.

So here, the article is used because the veterinarian is the subject of the sentence, not just a job label.

Yes. El veterinario refers to a male veterinarian.

If the vet were female, it would normally be:

• La veterinaria la va a esterilizar mañana.

So the noun and article together show the vet’s gender:

• el veterinario = male vet
• la veterinaria = female vet

In this context, yes, that is probably the best English translation.

Literally, esterilizar means to sterilize, but in veterinary contexts it is commonly used for pets being spayed or neutered.

For a female animal, English often specifically says spay. So:

• esterilizarla in this context would usually be understood as to spay her

In everyday Spanish, esterilizar is often a broad, neutral term. You may also hear castrar, though that can sound more specifically like castrate and is often associated with males.

Yes. That is completely correct.

Spanish allows both placements with this kind of verb phrase:

• El veterinario la va a esterilizar mañana
• El veterinario va a esterilizarla mañana

Both mean the same thing: The veterinarian is going to spay/sterilize her tomorrow.

Learners should get used to both patterns, because native speakers use both.

Yes, if the context already makes it clear who is being talked about.

For example:

• La va a esterilizar mañana.

Spanish often drops subjects when they are understood from context.

However, including El veterinario makes the sentence clearer and more explicit, especially if there could be confusion about who will do the action.

Grammatically, la can refer to any feminine direct object, including a woman, a feminine noun, or a female animal.

So by itself, la does not automatically mean female animal. The context does that.

In this sentence, because the verb is esterilizar and the subject is el veterinario, the most natural interpretation is that la refers to a female pet or animal.