This is the 816th most frequent Swedish word.
natt
"Night."
In this sentence, 'natt' is used as a noun in its definite form 'natten', referring specifically to 'the night'.
Natten var kall och stilla.
The night was cold and still.
Here, 'natt' appears in the definite form 'natten', part of an expression indicating a specific night duration.
Vi stannade uppe hela natten för att titta på stjärnorna.
We stayed awake all night to watch the stars.
This sentence uses 'natt' in a prepositional phrase 'om natten', meaning 'at night' and referring to the general nighttime.