This is the 223rd most frequent Portuguese word.
num
"Num" is the contraction of "em" (in/on/at) + "um" (a/an).
The usage of 'num' as a contraction of 'em um' again provides a succinct form to express a location in Portuguese.
Vamos nos encontrar num parque perto daqui.
Let’s meet at a park nearby.
Here, 'num' is a contraction of 'em um', meaning 'in a', indicating the location in a general sense.
Eu estava num restaurante ontem.
I was at a restaurant yesterday.
In this sentence, 'num' combines 'em' (in/on) with 'um' (a), specifying the item 'an old map' related to the action.