This is the 827th most frequent Turkish word.
sebebi
"Sebebi" means "the reason" or "the cause" in English.
Here, 'sebebiyle' is used as a postposition meaning 'due to/because of', indicating a reason for the following action.
Havanın soğuk olması sebebiyle içeride kalmayı tercih ettik.
Due to the weather being cold, we preferred to stay inside.
In this context, 'sebebi' means 'reason', explaining the cause behind the mentioned success.
Bu başarının sebebi sıkı çalışmak ve disiplinli olmaktır.
The reason for this success is hard work and discipline.
Here, 'sebebini' refers to 'the reason (for)', used in possessive form to inquire about the cause of the postponement.