A diary is a record (originally in handwritten format) with discrete entries arranged by date reporting on what has happened over the course of a day or other period. Diaries undertaken for institutional purposes play a role in many aspects of human civilization, including government records (e.g., Hansard), business ledgers and military records. Schools or parents may teach or require children to keep diaries in order to encourage the expression of feelings and to promote thought.
Generally the term is today employed for personal diaries, in which the writer may detail more personal information and normally intended to remain private or to have a limited circulation amongst friends or relatives. The writer may also describe recent events in his/her personal diary. The word "journal" may be sometimes used for "diary," but generally one writes daily in a diary, whereas journal-writing can be less frequent.
(from Wikipedia)
