A window includes a folding portion foldable with respect to an imaginary folding axis extending in a first direction, a first non-folding portion, and a second non-folding portion spaced apart from the first non-folding portion in a second direction perpendicular to the first direction with the folding portion interposed therebetween. The folding portion includes a base portion and a plurality of protrusion portions disposed on the base portion and spaced apart from each other in the second direction. A width, in the first direction, of the folding portion is smaller than a width, in the first direction, of each of the first non-folding portion and the second non-folding portion.