This is the 607th most frequent Serbian word.
њена
"Њена" means "her" or "hers" in English, indicating possession.
Here, 'њена' is a possessive adjective modifying the noun 'кућа' (house), indicating ownership.
Њена кућа је велика.
Her house is big.
In this sentence, 'њена' functions as a possessive pronoun following the verb 'је' (is) to indicate possession.
Књига је њена.
The book is hers.
Here, 'њена' acts again as a possessive adjective describing ownership of 'идеја' (idea).