Line symmetry of the alphabet occurs when a portion of a letter mirrors another portion. When the image is folded, the portions line up exactly. The line of the fold is considered the line of symmetry and can be horizontal or vertical.
Lines of symmetry in the alphabet depend on the font used and whether the letters are capitalized or lowercase. Capital letters in a standard font allow for symmetry in the following individual letters: A, B, C, D, E, H, I, K, M, O, T, U, V, W, X and Y. Some letters have rotational symmetry, meaning that the image looks the same when rotated. These include: H, I, N, O, S and Z.