A diary is a handwritten record with entries arranged by date reporting on what has happened over the course of a day or other period. A personal diary may include a person's experiences, thoughts, and/or feelings, excluding comments on current events outside the writer's direct experience. Diaries have also played a role in many aspects of human civilization, including government records, business ledgers, and military records.
Today, personal diaries are the most common and are normally intended to remain private or to be shared only with friends or relatives. A diary may, however, provide information for a memoir, autobiography or biography.
The word "journal" may be sometimes used for "diary," but generally a diary has (or intends to have) daily entries, whereas journal-writing can be less frequent.