Preposition 'Em': In, On, At | Portuguese (Brazil) Grammar

If you are an English speaker, em is the preposition that will feel suspiciously easy at first and then quietly betray you. English carefully distinguishes in (the box), on (the table), and at (the corner). Brazilian Portuguese throws all three into one word: em. The book is na mesa, the city is na Bahia, the meeting is na segunda — one preposition for all of it. The trade-off is that you have to stop translating in/on/at and just trust em — and you have to remember, as always, that em fuses with whatever article follows it.

Location: in, on, at — all em

The core job of em is to locate something in space. Where English would weigh whether to say in, on, or at, Portuguese reaches for em every time and lets context sort out the rest.

As chaves estão na mesa da cozinha.

The keys are on the kitchen table. (em + a = na)

Eu trabalho num escritório no centro.

I work in an office downtown. (em + um = num, em + o = no)

Ela mora no Brasil, numa cidade pequena do interior.

She lives in Brazil, in a small town in the countryside.

One special case English speakers love: "at home" is em casa — with no article, so no contraction. The bare em casa means "(at) home" as a general place; na casa points to a specific house.

Hoje eu vou ficar em casa o dia inteiro.

Today I'm going to stay home all day.

A festa vai ser na casa do Pedro.

The party is going to be at Pedro's house. (em + a = na)

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Don't ask yourself "is this in, on, or at?" — that's the English question. Ask "is something located somewhere?" If yes, the preposition is em, and then you just contract it with the article.

Time: years, months, days

Em also marks points in time — years, months, seasons, and (with the article) days of the week.

Eu nasci em 1995, em setembro.

I was born in 1995, in September.

A gente se vê na segunda, então.

See you on Monday, then. (em + a = na)

No verão a cidade fica cheia de turistas.

In the summer the city gets full of tourists. (em + o = no)

Notice the split: bare years and months take plain em (em 1995, em setembro), but days of the week take a contracted form because they carry an article (na segunda, no domingo). This mirrors how Brazilians think of weekdays as feminine nouns: a segunda(-feira), o domingo.

Transport: on the bus, by car

To say you travel on or by a means of transport, Brazilian Portuguese uses em (contracted) for vehicles you get inside of.

Eu vou pro trabalho no ônibus todo dia.

I go to work on the bus every day. (em + o = no)

A gente foi pra praia no carro do meu tio.

We went to the beach in my uncle's car.

There is a competing pattern with de for the bare means — de ônibus, de carro, de avião — which answers "how?" (de ônibus = by bus, as a method). Use de + bare noun for the general method, and em/no when there's a specific vehicle (no ônibus das sete, no carro do tio).

The contractions of em

Em never stands next to an article. Burn this table in.

em +	contraction	example
o	no	no carro
a	na	na mesa
os	nos	nos livros
as	nas	nas mãos
ele / ela	nele / nela	pensei nela
eles / elas	neles / nelas	confio neles
isso / isto / aquilo	nisso / nisto / naquilo	não acredito nisso
este / esse / aquele	neste / nesse / naquele	moro nesse prédio
um / uma	num / numa (informal)	num lugar qualquer

Pendurei o casaco naquele cabide ali.

I hung the coat on that hanger over there. (em + aquele = naquele)

Eu não acredito nisso de jeito nenhum.

I don't believe that at all. (em + isso = nisso)

Verbs that take em

Just as gostar drags de behind it, several common verbs require em. The big two for beginners are pensar em (to think about) and acreditar em (to believe in). English uses about and in there — but you have to override that and reach for em, which then contracts.

Verb + em	Meaning
pensar em	to think about
acreditar em	to believe in
confiar em	to trust
mexer em	to touch / mess with
insistir em	to insist on
reparar em	to notice

Eu fico pensando em você o dia todo.

I keep thinking about you all day.

Pode confiar nele, ele nunca falha.

You can trust him, he never lets you down. (em + ele = nele)

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When a verb takes em and the object is a pronoun, you get the fused forms nele, nela, neles, nelas: pensei nela (I thought about her), confio neles (I trust them). This catches English speakers off guard because "in him / about her" looks nothing like a single fused word.

Common Mistakes

❌ Eu moro em o Rio.

Incorrect — em + o must contract to no.

✅ Eu moro no Rio.

I live in Rio.

❌ O livro está sobre a mesa.

Not wrong, but overly formal — sobre means 'on top of/about'; everyday speech uses na for 'on the table'.

✅ O livro está na mesa.

The book is on the table.

❌ Eu penso sobre você.

Incorrect — pensar takes em, not sobre, for 'think about (someone)'.

✅ Eu penso em você.

I think about you.

❌ A reunião é em a segunda.

Incorrect — em + a must contract to na.

✅ A reunião é na segunda.

The meeting is on Monday.

❌ Eu não acredito em isso.

Incorrect — em + isso must contract to nisso.

✅ Eu não acredito nisso.

I don't believe that.

Key Takeaways

Em covers English in, on, and at for both place and time — stop translating and just locate the thing.
It contracts obligatorily: no, na, nos, nas with articles; nele, nela, nisso, naquele with pronouns and demonstratives.
"At home" is bare em casa; a specific house is na casa de....
Use no/na for a specific vehicle (no ônibus), but de + bare noun for the general method (de ônibus).
Pensar em and acreditar em require em (which contracts to nele/nisso) — memorize them as chunks.

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