O gato está debaixo da mesa.

Here is the breakdown:

• o = the for a masculine singular noun
• gato = cat
• está = is from the verb estar
• debaixo de = under / underneath
• da = contraction of de + a
• mesa = table

So the structure is literally:

• O gato = the cat
• está debaixo da mesa = is under the table

A very literal word-for-word version would be something like The cat is underneath of-the table, but in natural English we just say The cat is under the table.

Portuguese has two verbs that can both translate as to be:

• ser
• estar

In this sentence, estar is used because it describes a location or temporary state.

So:

• O gato está debaixo da mesa = the cat is under the table

That is about where the cat is, not what the cat is.

Compare:

• O gato é preto. = The cat is black.
• O gato está debaixo da mesa. = The cat is under the table.

A useful beginner rule is:

• ser → identity, characteristics, time, origin
• estar → location, condition, temporary state

The key expression is debaixo de, which means under / underneath.

So:

• debaixo de + a mesa → debaixo da mesa

This is very common in European Portuguese.

You can think of debaixo de as a fixed expression. It is not usually translated piece by piece in a useful way for beginners; it is best learned as a chunk:

• debaixo de = under

Portuguese often uses multi-word prepositional expressions where English uses a single preposition.

Because in Portuguese, de + a normally contracts to da.

So:

• de + a mesa → da mesa

This kind of contraction is extremely common.

Some useful ones:

• de + o = do
• de + a = da
• em + o = no
• em + a = na
• a + o = ao
• a + a = à

So debaixo da mesa is really:

• debaixo de a mesa → debaixo da mesa

But the uncontracted version sounds wrong in normal Portuguese.

Portuguese uses definite articles very naturally and often more regularly than English.

In this sentence:

• o gato = the cat
• a mesa = the table

Because we are talking about a specific cat and a specific table, the articles are normal and expected.

In many contexts, leaving the article out would sound unnatural or would change the meaning.

For example:

• O gato está debaixo da mesa. = The cat is under the table.
• Gato by itself usually means cat in a more general or dictionary-like sense.

English sometimes drops articles where Portuguese keeps them, so this is something learners need to get used to.

You have to learn the gender of each noun as part of the word.

In this sentence:

• gato is masculine → o gato
• mesa is feminine → a mesa

This affects:

• the article: o / a
• sometimes adjectives too: preto / preta, bonito / bonita, etc.

A helpful pattern is that many nouns ending in -o are masculine and many ending in -a are feminine, but this is only a tendency, not a guaranteed rule.

So it is best to learn nouns together with their article:

• o gato
• a mesa

Gato can mean:

1. a male cat, specifically
2. cat in a general sense, depending on context

If you want to make it clearly female, you would say:

• a gata = the female cat

So:

• O gato está debaixo da mesa. can mean The cat is under the table without focusing on sex, or it can specifically mean The male cat is under the table, depending on context.
• A gata está debaixo da mesa. = The female cat is under the table.

This is quite common in Portuguese: the masculine form can sometimes be used generically.

Yes, sob also means under, so:

• O gato está sob a mesa.

is grammatically correct.

However, there is a style difference:

• debaixo de is very common and natural in everyday speech
• sob is shorter and correct, but often feels a bit more formal, literary, or less conversational

For a beginner learning everyday European Portuguese, debaixo da mesa is usually the more useful phrase to remember first.

If you are learning Portuguese from Portugal, it is better to stick with debaixo da mesa.

Why?

• debaixo de is the standard, everyday choice in European Portuguese
• embaixo de is much more strongly associated with Brazilian Portuguese

A Portuguese learner who wants Portugal Portuguese should treat debaixo de as the safest default.

So in Portugal:

• O gato está debaixo da mesa. = the natural choice

The normal, neutral order is:

• O gato está debaixo da mesa.

That is the best version for most situations.

But Portuguese can change word order for emphasis or style. For example:

• Debaixo da mesa está o gato.

This is grammatical, but it sounds more marked, literary, or emphatic, as if you are highlighting under the table.

For everyday speech, use:

• subject + verb + location

So the standard pattern is:

• O gato
  • está
    • debaixo da mesa

In European Portuguese, está is pronounced roughly like shtah, though that is only an approximation.

A few useful points:

• the initial es- in many words often sounds closer to sh to English ears in Portugal
• the stress is on the last syllable: es-TÁ
• the written accent mark on á shows the stressed vowel

So:

• está ≈ shtah

But native European Portuguese pronunciation is quite reduced compared with spelling, so listening practice is especially important.

A rough learner-friendly approximation is:

• u GA-tu sh-TA də-BAI-shu dɐ ME-zɐ

A more IPA-like version is approximately:

• [u ˈɡatu ʃˈta dɨˈbajʃu dɐ ˈmezɐ]

A few things that may surprise an English speaker:

• o often sounds close to u
• unstressed e is often reduced, sometimes sounding like uh or ih
• s before t often sounds like sh
• final vowels are often weaker than learners expect

European Portuguese pronunciation can sound much more compressed than the spelling suggests.

It is most commonly used for physical position:

• O gato está debaixo da mesa.

That is the clearest and most basic use.

It can sometimes be extended metaphorically, but for beginners it is best to think of debaixo de mainly as a physical location expression meaning under or underneath.

So if you see:

• debaixo da cama = under the bed
• debaixo da cadeira = under the chair
• debaixo da mesa = under the table

that is exactly the same pattern.

You would make both the noun and the verb plural:

• Os gatos estão debaixo da mesa.

Changes:

• o → os
• gato → gatos
• está → estão

But da mesa stays the same because there is still just one table:

• Os gatos estão debaixo da mesa.

If it were the tables, then it would become:

• debaixo das mesas

because:

• de + as = das