What are letters that have a rotational symmetry?

Letters with rotational symmetry are those that look the same when rotated 180 degrees. In the English alphabet, examples include the letters H, I, O, S, X, and Z. These letters maintain their appearance regardless of being flipped upside down. Other letters, such as A, M, T, U, V, W, and Y, exhibit symmetry when rotated 180 degrees, but only in specific contexts or fonts.