This is the 7th most frequent Portuguese word.
na
"Na" is the contraction of "em" (in/on/at) + "a" (the, feminine).
Here, 'na' is a contraction of 'em' (in) and 'a' (the, feminine), indicating location.
Ela está na sala.
She is in the room.
In this sentence, 'na' again represents the contraction of 'em' (at) and 'a' (the, feminine), referring to attending a specific event.
Nós estaremos na reunião amanhã.
We will be at the meeting tomorrow.
Here, 'na' combines 'em' (on) with 'a' (the, feminine), pointing to the item's placement on the surface.