This is the 5907th most frequent French word.
dan
A rank in martial arts.
In this sentence, 'dans' is used as a preposition indicating location—specifically 'in.' It specifies that the book is inside the box.
Il y a un livre dans la boîte.
There is a book in the box.
Here, 'dans' serves as a preposition again but now indicating where the dancing activity is taking place—'in the room.'
Il danse dans la salle.
He dances in the room.
In this example, 'dans' denotes the location where the walking will happen—'in the park.' It continues to serve its role as a preposition indicating 'inside.'