This is the 13823rd most frequent Turkish word.
liderinin
"Of their leader" or "their leader's."
The word 'liderinin' is the possessive form referring to 'the leader's' in relation to the team.
Takım liderinin önerisini tartıştık.
We discussed the team leader's suggestion.
The word 'liderinin' expresses possession, in this case referring to 'the leader's speech' as owned by the leader.
Dün liderinin konuşmasını dinledim.
Yesterday, I listened to the leader's speech.
Here, 'liderinin' denotes possession, indicating that the actions were directed by 'the leader's' instructions.