This is the 6396th most frequent Polish word.
będący
"Being"
Here, 'będący' describes the painting, indicating its state or role as a masterpiece.
Widziałem obraz będący arcydziełem.
I saw a painting being a masterpiece.
Here, 'będąca' serves as a present participle meaning 'being', describing the book's state.
Książka będąca na stole należy do mnie.
The book being on the table belongs to me.
In this sentence, 'będący' functions as an adjective that conveys a continual state or characteristic.