Source : Webster's Revised Unabridged Dictionary (1913)

Diary \Di"a*ry\, n.; pl. {Diaries}. [L. diarium, fr. dies day.
   See {Deity}.]
   A register of daily events or transactions; a daily record; a
   journal; a blank book dated for the record of daily
   memoranda; as, a diary of the weather; a physician's diary.