This is the 123rd most frequent Bulgarian word.
български
Bulgarian; relating to Bulgaria or its language.
The word 'български' is used here as an adjective to describe the language 'език', indicating the Bulgarian language.
Аз уча български език.
I am learning Bulgarian.
Here, 'български' qualifies 'народен танц' (folk dance), indicating that it originates from Bulgaria.
Това е български народен танц.
This is a Bulgarian folk dance.
In this context, 'български' stands alone as a noun representing the Bulgarian language in informal usage.