This is the 485th most frequent Swedish word.
ulf
The word "ulf" is an old Swedish form of "wolf" (a carnivorous mammal) and is also used as a male given name in Sweden.
Here, 'Ulf' is a proper noun, specifically a given name typically used for males.
Ulf är en vänlig person.
Ulf is a friendly person.
In this sentence, 'ulv' means 'wolf' in Swedish. It is used as a noun referring to the animal.
En ulv smög genom skogen.
A wolf sneaked through the forest.
Again, 'ulv' refers to 'wolf', used as a subject in this sentence to describe the action of howling.