This preposition is usually a bit easier to understand compared to others. Although there are multiple uses, it most commonly refers to being “in” something, either physically or conceptually:
Estamos em Setembro We are in September
Ela está em Lisboa She is in Lisbon
Ela divide o quarto em dois She divides the room in two
Estar em dúvida To be in doubt
Ele está em boa condição física. He is in good physical condition.
Ela está em choque She is in shock
“Em” can also have other meanings, for example:
When “em” is combined with the articles a, o, as, or os they become na, no, nas, or nos
Estou na garagem I am in the garage
O jantar está na mesa Dinner is on the table
Tu pensas nas tuas amigas You think about your friends
Os livros estão nas caixas The books are in the boxes
Eles vivem no Japão They live in Japan
“Em” is also commonly combined with the third-person personal pronouns ele, ela, eles and elas, to become nele, nela, neles and nelas.
These contractions may define a position in relation to an object or subject, and as you’d expect, they also agree in gender and quantity with the noun they describe.
They also have other uses, as shown below: