O animal de estimação está em casa.

O is the masculine singular definite article, so o animal de estimação means the pet.

If you wanted a pet, you would normally say um animal de estimação.

Portuguese uses articles very regularly, so learners often notice them more than in English.

De estimação is the expression that means pet or, more literally, kept as a companion.

So:

• animal = animal
• de estimação = kept as a pet / pet-related

Together, animal de estimação = pet

This is a fixed expression. You usually learn it as a chunk.

It often can. In Brazil, people also say:

• pet — very common in everyday speech
• bicho de estimação — also common and natural
• animal de estimação — correct, clear, slightly more neutral or formal

So this sentence is perfectly natural, but in casual Brazilian Portuguese, many people would simply say O pet está em casa.

Portuguese has two main verbs for to be: ser and estar.

Here, está is used because being at home is seen as a location or temporary state.

• ser = for identity, permanent characteristics, origin, time, etc.
• estar = for location, condition, temporary states

So:

• O animal de estimação está em casa. = The pet is at home.

Using é here would sound wrong.

Em casa is the normal expression for at home.

It works like an idiomatic phrase:

• estou em casa = I’m at home
• ele está em casa = he is at home

But na casa usually means in/at the house of someone or in a specific house:

• Estou na casa da minha avó. = I’m at my grandmother’s house.
• O animal está na casa do vizinho. = The animal is at the neighbor’s house.

So:

• em casa = at home
• na casa = in/at the house

Here it means home.

Portuguese casa can mean both house and home, depending on context.

In the expression em casa, the meaning is usually at home, not just physically inside a building.

Animal is grammatically masculine in Portuguese, so it takes o in the singular:

• o animal
• os animais

This is grammatical gender, not necessarily biological sex.

So even if the pet is female, you can still say o animal, because the noun animal is masculine.

If you want to show the animal’s sex more clearly, you would usually use a more specific noun:

• a gata = the female cat
• a cadela = the female dog
• a coelha = the female rabbit

It becomes:

Os animais de estimação estão em casa. = The pets are at home.

Notice the changes:

• o → os
• animal → animais
• está → estão

But de estimação stays the same.

Yes, sometimes.

Portuguese often drops the subject when it is clear from context. So if everyone already knows you are talking about the pet, Está em casa can be enough.

However, the full sentence O animal de estimação está em casa is clearer and better for learners to study.

Estimação is pronounced roughly like es-chee-ma-SOWN in Brazilian Portuguese, though the exact sound depends on accent.

The accent mark in -ção helps show the stressed syllable and is part of a very common ending in Portuguese.

Examples:

• estimação
• informação
• situação

That -ção ending is very common and often corresponds to English -tion.

A rough pronunciation guide is:

oo ah-nee-MAHL djee es-chee-ma-SOWN es-TAH ẽ KAH-zah

A few helpful notes:

• O often sounds like oo
• de before e/i in many Brazilian accents sounds like djee
• está has stress on the last syllable: -tá
• em is nasal
• casa sounds like KAH-zah

A natural Brazilian rhythm is smoother than the spelling may suggest, so it is best to listen to native audio too.

The normal, neutral order is:

O animal de estimação está em casa.

That is the most natural way to say it in most contexts.

Portuguese can change word order for emphasis, but that is less basic and often less natural for beginners. For example, Em casa, o animal de estimação está sounds marked or literary.

So for everyday speech, keep the standard order: subject + verb + place

It is neutral and completely correct.

Depending on the situation, Brazilians might say more casual versions like:

• O pet está em casa.
• O bichinho está em casa. — more affectionate, depending on context

But O animal de estimação está em casa is standard, clear Portuguese.