A window for a display device including: a plastic substrate including a poly(imide-amide) copolymer, which is a reaction product of a reagent combination of 4,4′-hexafluoroisopropylidene diphthalic anhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2′-bis-trifluoromethyl-4,4′-biphenyldiamine, and terephthaloyl chloride, and a hard coating layer disposed on at least one side of the plastic substrate, wherein the plastic substrate has pencil scratch hardness of greater than or equal to 3H when measured according to an ASTM D3363 standard at a vertical load of about 0.5 kilograms, and a peak intensity ratio A2/A1 of a peak intensity A2 at a position of about 23.5° in 2θ to a peak intensity A1 at a position of about 15.5° in 2θ of an X-ray diffraction spectrum is greater than or equal to about 0.8.