This is the 426th most frequent Turkish word.
babası
"His/her/their father."
In this sentence, 'babası' means 'his/her father' and indicates possession of 'baba' (father) by implying 'his/her' with the suffix '-ı'. The subject is singular and third person.
Babası işe gidiyor.
His/Her father is going to work.
Here, 'babası' indicates possession, with the inclusion of 'Ahmet'in' ('Ahmet's') specifying whose father is being referred to. The suffix '-ı' still indicates third person.
Ahmet'in babası koyunlarını otlatıyor.
Ahmet's father is grazing the sheep.
In this example, 'babası' continues to mean 'his/her father', with the context of youth appearance. It emphasizes the possessive (implicit 'his/her') and third-person usage.