Yes, it can. However, it must be creative and catch the reader's attention, and not start with a boring "Dear Diary". It can be a very interesting way of narrative writing.
It is spelled Dear Diary.
his diary
Kim's diary = the diary that belongs to Kim
Diary - 2000 Diary of Ludacris was released on: USA: 2002
Who keeps a Diary? The diary was full with secrets.
Diary - 2000 Best of Diary was released on: USA: 1 February 2001
The most famous diary is Anne Frank's diary.
Her diary is called, "A Diary of a Young Girl".
The plural of diary is diaries.
Anne received the diary on her birthday. She wrote about receiving the diary and her birthday and the problems in Belgium and her life.
Diary - 2000 Diary of Tony Hawk was released on: USA: March 2003
Diary - 2000 The Diary of Lindsay Lohan was released on: USA: March 2004