the act of developing or disclosing that which is unknown; a gradual unfolding process by which anything is developed, as a plan or method, or an image upon a photographic plate; gradual advancement or growth through a series of progressive changes; also, the result of developing, or a developed state.-the series of changes which animal and vegetable organisms undergo in their passage from the embryonic state to maturity, from a lower to a higher state of organization.-the act or process of changing or expanding an expression into another of equivalent value or meaning.-the equivalent expression into which another has been developed.-the elaboration of a theme or subject; the unfolding of a musical idea; the evolution of a whole piece or movement from a leading theme or motive.