This is the 13672nd most frequent Swedish word.
vietnamesiska
Vietnamese (language).
Here, 'vietnamesiska' is used as a noun to denote the Vietnamese language.
Jag studerar vietnamesiska vid universitetet.
I study Vietnamese at the university.
In this sentence, 'vietnamesiska' is treated as a noun referring to the language being spoken.
Min vän talar vietnamesiska med sin familj.
My friend speaks Vietnamese with their family.
Here, 'vietnamesiska' is used as part of an adjective phrase 'den vietnamesiska kulturen' describing the culture related to Vietnam.