This is the 4598th most frequent Turkish word.
beli
"Waist."
Here, 'beli' is a possessive form (his/her) of 'bel,' meaning 'back' or 'waist', and it is used to describe physical discomfort.
Onun beli ağrıyor.
His/her back is aching.
In this sentence, 'belli' means 'certain' or 'clear,' used to express uncertainty.
Başarıyı elde etmek için bunu yapabilecek mi, henüz belli değil.
It's not certain yet whether he/she can do this to achieve success.
Here again, 'belli' conveys the meaning of 'certain' in terms of outcomes or situations.