Pastoral poetry is a genre defined primarily by subject matter. The term derives from the Latin "pastor" meaning shepherd; it is synonymous with "bucolic", derived from a Greek term meaning "cowherd". The conventions of the pastoral were first established in the "Idylls" of Theocritus, an Hellenistic poet. The setting of pastoral poems is rural and the main characters are shepherds, shepherdesses, and farmers. The setting and characters are idealized, portrayed as living a simple, almost Edenic life, of innocence. Often the major plots revolve around love or the intrusion of a city-dweller into the pastoral landscape. The tone is often nostalgic.