This is the 5455th most frequent Turkish word.
ların
"ların" is a plural possessive suffix in Turkish meaning "of theirs" or "of them."
The word 'ların' indicates possession and shows that the books belong to a group or context.
Kitapların nerede olduğunu biliyor musun?
Do you know where the books are?
The word 'larının' in the sentence refers to the possession or relation with 'friends', indicating what they say.
Arkadaşlarının söylediklerine dikkat et.
Pay attention to what your friends are saying.
The word 'lerinin' is derived from 'ların', used here to indicate possession or relationship with 'gardens' belonging to the house.