In Portuguese, contractions are used quite frequently, especially to combine prepositions and articles.
I think learning the contractions are very important, since sometimes it is tricky to recognize them when listening to conversations in Portuguese.
For example, the word "em" (meaning "in", "at", and sometimes "on") must be contracted when before a definite article:
em + o = no
em + a = na
em + os = nos
em + as = nas
Here are some sentences:
1. Eu estou no carro. (I am in the car.)
2. Ela mora no Brasil. (She lives in Brazil.) *
3. Ele trabalha na fábrica. (He works in the factory.)
4. Onde eles estão? Na biblioteca. (Where are they? In the library.)
*- Most countries have a definite article in front of them in Portuguese. For example: o Brasil, os Estados Unidos.
Most cities do not have articles: em Nova Iorque (in New York), em São Paulo. However, no Rio de Janeiro is one exception.
