The Dear Diary lexicon is actually a square, white laptop computer. The spine is light grey and there is a black Nobody symbol adorning the lower right corner of the laptop. When opened up, the keys are shown to be black and its wallpaper is red background with a black Nobody symbol on the right side. Seeing as this weapon represents Zexion's personality, it may be reference to how secretive he is.
A diary is a daily log of personal experiences. Diaries are often, but not always, kept secret and personal to the writer. The phrase “Dear Diary” is a stereotypical header for a diary entry. “Notebook” can either refer to an actual book which notes are written in, or a type of laptop computer.
Dear Diary's normal ground combo consists of a slash straight down with the spine down, then a sweep from Zexion's upper right to lower left and back, and a sweeping spin that serves as the finisher. The -Combo chain consists of a sweep from Zexion's upper right to lower left and back, the latter of which sends Zexion up into the air, and flinging the Dear Diary forwards while spinning.
The aerial combo consists of two vertical strikes, one down and one up, and finally spinning the Dear Diary forwards for the finisher.
When Dear Diary strikes an enemy, purple lightning emanates from the strike point, with purple bar lines and digits appearing after the ground combo finisher. When it strikes a wall, small yellow stars spread out.