1. A daily record of events or transactions, a journal: Specifically, a diary consists of daily records of matters affecting the writer personally, or which come under his or her personal observations.
2. A book which is set up for keeping a daily record, or having spaces with printed dates for certain daily memoranda and keeping notes about topics: Some diaries also include calendars that contain daily contents about matters of importance to people generally, or to members of a particular profession, occupation, or pursuit.