Learn Hardcore Portuguese (Portugal): O Pedro guarda os seus livros na estante.

You can drop the article in some contexts (e.g. in very formal language, in lists, in some fixed expressions), but in normal conversation in Portugal, O Pedro is perfectly standard and expected.

Note: In Brazilian Portuguese, using the article with names is less consistent and more regional; in Portugal it’s broadly standard.

Why is the verb guarda and not guardar or guardo?

guardar is the infinitive: to keep / to store / to put away.
guarda is the 3rd person singular, present tense of guardar:
- eu guardo – I keep
- tu guardas – you (informal singular) keep
- ele / ela / o Pedro guarda – he / she / Pedro keeps

Because the subject is O Pedro (3rd person singular), the correct form is guarda:

O Pedro guarda… = Pedro keeps / puts away…

What exactly does guardar mean here? Is it “keep”, “store”, or “put”?

Guardar is quite flexible. It can mean:

to keep / to store something somewhere:
- O Pedro guarda os seus livros na estante.
  → He keeps his books on the shelf.
to put something away:
- Guarda os brinquedos.
  → Put the toys away.
to save / set aside:
- Guarda-me um bolo.
  → Save a cake for me.
to guard / watch over (more literal/protective sense):
- O polícia guarda o edifício.
  → The policeman guards the building.

In your sentence, the natural reading is “keeps / stores / puts (his books) away” on the shelf/bookcase.

Why is it os seus livros and not just seus livros?

In European Portuguese, possessives are usually used with a definite article:

os seus livros – his (or her / their) books
o seu livro – his (or her / their) book
a sua casa – his/her/their house

Saying just seus livros (without os) is possible in poetry, very formal language, or some fixed expressions, but in everyday European Portuguese you almost always include the article.

So:

O Pedro guarda os seus livros na estante. ✅ (natural)
O Pedro guarda seus livros na estante. ⚠️ sounds odd/overly formal in European Portuguese.

How do I know that seus means “his” and not “her” or “their”? It seems ambiguous.

Grammatically, seu / sua / seus / suas are 3rd‑person possessives and can mean:

his, her, its, their – depending on context.

In the sentence:

O Pedro guarda os seus livros na estante.

we understand seus as “his” only because the context tells us we are talking about Pedro.

If there’s any risk of ambiguity, Portuguese often avoids seu / sua / seus / suas and uses dele / dela / deles / delas instead:

os livros dele – his books
os livros dela – her books
os livros deles – their books (masc./mixed)
os livros delas – their books (fem.)

So you could also say:

O Pedro guarda os livros dele na estante.
→ Pedro puts his books on the shelf.

Both os seus livros and os livros dele are correct; os livros dele is clearer when more than one possible owner is in the context.

Why is it seus and not seu?

Possessive adjectives agree with the noun they modify, not with the owner.

livro (book) → masculine singular
- o seu livro – his/her/their book
livros (books) → masculine plural
- os seus livros – his/her/their books

So:

seu – masc. singular (for a singular masculine noun)
seus – masc. plural (for a plural masculine noun)
sua – fem. singular
suas – fem. plural

Because livros is plural masculine, we must use seus.

Could I say os livros dele instead of os seus livros? Is there any difference?

Yes, both are grammatical:

O Pedro guarda os seus livros na estante.
O Pedro guarda os livros dele na estante.

Meaning: Both usually mean “Pedro keeps his books on the shelf.”

Difference in feel:

os seus livros
- More compact and slightly more formal/written.
- Can be ambiguous if there are many people in the context.
os livros dele
- Often clearer in conversation, especially when several people are involved, because dele clearly points to a specific male person mentioned.

In European Portuguese, speakers very often choose dele / dela to avoid ambiguity.

Why is the article os there at all? Why not just Pedro keeps his books on the shelf without “the”?

Portuguese often uses definite articles where English does not.

With possessives in European Portuguese, you normally use:

article + possessive + noun
- os seus livros – literally “the his books”
- a minha casa – “the my house” → my house
- o nosso filho – our son

So:

os seus livros = “his books” in English, even though literally it has “the”.

Leaving out the article (seus livros) is grammatically possible but, as mentioned before, it sounds marked or unusual in everyday European Portuguese.

What does na estante mean exactly? Is it “in the shelf” or “on the shelf”?

na is a contraction of the preposition em (in/on/at) + the feminine singular article a (the):

em + a = na

estante (feminine) can be:

a shelf
a bookcase (depending on context and region)

So na estante is literally “in/on the shelf/bookcase”. In natural English you’d usually say:

on the shelf
in the bookcase

Portuguese em covers English “in”, “on”, and “at”, and the specific translation depends on the object and context.

Why na estante and not em a estante written separately?

In Portuguese, many prepositions contract with the definite articles. For example:

em + a = na
em + o = no
em + as = nas
em + os = nos

So instead of writing:

em a estante ❌

you must contract it:

na estante ✅

This contraction is obligatory in standard written and spoken Portuguese.

Does O Pedro guarda os seus livros na estante mean he is doing it right now, or that he usually does it?

The present tense in Portuguese is flexible, like in English:

It can describe a habit / general truth:
- O Pedro guarda os seus livros na estante.
  → Pedro keeps (usually stores) his books on the shelf.
It can also be used for something happening right now, especially if supported by context, although for “right now” European Portuguese often prefers the progressive:
- O Pedro está a guardar os seus livros na estante.
  → Pedro is putting his books on the shelf (right now).

So your sentence most naturally suggests a habitual or general behaviour, but context can push it towards a present action.

If I replace os seus livros with a pronoun, how would the sentence look?

The direct object pronoun for os livros (masculine plural) is os.

In European Portuguese, in a simple affirmative statement, the unstressed object pronoun typically goes after the verb, with a hyphen (this is called enclisis):

O Pedro guarda-os na estante.
→ Pedro keeps them on the shelf.

Some patterns:

Ele lê os livros. → Ele lê-os.
O Pedro guarda os seus livros. → O Pedro guarda-os.

Word order can change with negation, some adverbs, etc., but in this straightforward case, the pronoun attaches to the verb.

Is there any difference between estante and prateleira?

Yes:

estante usually means:
- a bookcase or shelving unit (often with several levels), sometimes also a large shelf.
prateleira usually means:
- a single shelf (one horizontal surface).

So:

na estante – in/on the bookcase (or shelving unit)
na prateleira – on the shelf (one level)

In many contexts, people still understand estante as “shelf”, but prateleira is the more precise word for a single shelf board.