This is the 1116th most frequent Turkish word.
eşinin
"Of his/her spouse" or "of their spouse."
Here, 'eşinin' means 'of your spouse' and shows possession.
Eşinin fikrini dinlemelisin.
You should listen to your spouse's opinion.
'Eşinin' in this sentence indicates 'your spouse's,' showing possession of the birthday party.
Eşinin doğum günü partisi için bir hediye aldım.
I bought a gift for your spouse's birthday party.
In this example, 'eşinin' refers to 'spouse's' to denote possession of the company they work at.