It falls into the action category
it's a preposition
Adjective
Sudden is an adjective.
If you mean the part of speech, it is a noun. If you mean the etymology, it comes from Greek.
The word "you" belongs to the pronoun word class, particularly as a second person singular pronoun. It is used to refer to the person or people being spoken to.
Ornithologist.
Tigers belong to Class Mammalia.
Opossums belong to the class mammalia.
They belong to the class Mammalia ( mammals).
the priests belong to the upper class (1st class)
the priests belong to the upper class (1st class)
A piranha belong to the Phylum Chordata, and the class Osteichthyes.