What is the sentence of diary?

A diary doesn't have a sentence. It's a book or notebook used for keeping a personal record of experiences, thoughts, and feelings.

Perhaps you are asking about a sentence you might write in a diary. Here are some examples:

* "Today was a long and tiring day."

* "I'm so excited about the upcoming trip!"

* "I'm feeling really stressed about my upcoming exams."

Let me know if you have another question!