What EM and DE actually mean
Two of the most common words in Portuguese:
em = in / on / at — where something is: em casa (at home), em São Paulo (in São Paulo).
de = of / from — origin and belonging: de Londres (from London), a casa de Maria (Maria's house — "the house of Maria").
Here is the rule this page exists for: when em or de meets the little words o, a, os, as (the), they are NOT allowed to stand apart. They MUST merge into one word. "Em o Brasil" is as wrong in Portuguese as "childs" is in English.
The full merge table
| + o | + a | + os | + as | |
|---|---|---|---|---|
| em | no | na | nos | nas |
| de | do | da | dos | das |
When you'll use each one
| Eu moro no Brasil. | em + o Brasil → no (location) |
| Ela está na praia. | em + a praia → na (location) |
| Gosto do café do Brasil. | de + o → do (liking + origin) |
| nove da manhã | de + a manhã → da (time of day) |
| As chaves estão nas casas. | em + as → nas (plural works the same) |
When there is NO merge — the exceptions
The merge only happens when there is an article to merge WITH. Many places take no article:
| Moro em São Paulo. | most CITIES take no article → bare em |
| Estou em casa. | "at home" — fixed expression, no article |
| Sou de Londres. | city again → bare de |
| but: Moro no Rio de Janeiro. | o Rio is the famous exception — it carries its article |
Why Portuguese does this
Say "em o" out loud fast — your mouth naturally slides to "no". The contractions are simply spelling what every mouth already does. That is why they are mandatory: writing "em o" would be writing something nobody says.
Practise this chapter
5 pool questions plus generated ones — 20 fresh practice questions, reshuffled every visit, inside the grammar library.
Practise Contractions: no, na, do, da — 20 questions →This chapter is taught in Lição 2 of the course — free, no account needed. Rumo is a complete Brazilian Portuguese course, A1 to B2; level A1 is free.