Dyestuff yog ib yam khoom uas muaj xim uas muaj chemically bonds rau lub substrate uas nws yog siv.Feem ntau dyes yog hluavtaws, piv txwv li, yog man-made los ntawm petrochemicals.Lwm yam tshaj li pigmentation, lawv muaj ntau yam kev siv xws li organic dye lasers, optical media (CD-R) thiab lub koob yees duab sensors (xim lim array).