This is the 8787th most frequent Turkish word.
sendikasına
"To his/her/its union" or "to the union of him/her/it."
In this sentence, 'sendikasına' refers to a specific workers' union to which Ahmet became a member ('sendika' meaning 'union' and '-sına' indicating membership in or association with).
Ahmet işçi sendikasına üye oldu.
Ahmet became a member of the workers' union.
Here, 'sendikasına' conveys reliance or trust placed in a specific union as a collective entity that supports the women ('sendika' indicating the union and '-sına' denoting direction or association of trust).
Kadınlar haklarını savunmak için sendikasına güvendi.
The women relied on their union to defend their rights.
In this example, 'sendikasına' signifies the largest union in the country that is being considered as a potential entity to associate with or join ('sendika' referring to union and '-sına' suggesting affiliation towards).