This is the 1389th most frequent Turkish word.
yağı
"Yağı" in Turkish means "oil" or "fat."
In this sentence, 'yağı' refers to 'oil,' derived from 'yağ,' and is in the genitive case due to its relation to 'zeytin' (olive).
Salataya biraz zeytin yağı ekledim.
I added some olive oil to the salad.
Here, 'yağı' means 'oil,' referencing engine oil, with 'yağ' modified for the possessive 'motorun' (engine's).
Motorun yağı azalıyor; kontrol etmelisin.
The oil in the engine is running low; you should check it.
In this case, 'yağı' is poetically used to describe 'the lead' of a bullet ('kurşun'), showcasing its flexibility.