This is the 689th most frequent Norwegian word.
natt
"Night."
The word 'natt' is used as a noun to refer to 'night', the period of time after sunset and before sunrise.
Det var en stille natt.
It was a quiet night.
'Natten' is the definite form of 'natt' used to describe a specific night.
Hun jobbet hele natten.
She worked the whole night.
Here, 'natt' is used with 'i' to indicate an action that took place during the previous night.