Motives quickly define the key and rhythmic structure.
Good motives have some distinctive melodic or rhythmic feature that gives them interest and makes them recognizable throughout a composition. The imitation may begin immediately after the last note of the motive in the first voice, or it may overlap slightly. Or, a countermotive may be used. It has melodic interest of its own, yet compliments the motive, rhythmically. The episode functions in modulating from the key of the statement to the next key, and provides relief from full statements of the motive.