This is the 764th most frequent Slovenian word.
sina
The Slovenian word "sina" means "son" in English.
In this sentence, 'sina' is the accusative singular form of 'sin', which means 'son' in Slovenian.
Moj sina je star dvanajst let.
My son is twelve years old.
Here, 'sina' is also the accusative singular form and is used as the direct object of the verb 'obiskala'.
Obiskala sem sina v njegovem domu.
I visited my son at his home.
In this case, 'sina' again appears as the accusative, showing whom the action of 'gleda' pertains to.