The capital letters A, M, T, U, V, W and Y are vertically symmetrical, the capital letters B, C ,D, E and K are horizontally symmetrical, the capital letters H, I and X are both horizontally and vertically symmetrical, and the letter O is infinitely symmetrical. Symmetry is when something has exactly the same shape on either side of an axis line.
Words spelled exclusively with symmetrical letters can also be symmetrical. For instance, when spelled with capital letters, the words "BEDECKED," "BOOHOOED," "CHECKBOOK" and "DECIDED" are horizontally symmetrical. Vertically symmetrical words include "OTTO," "MAAM" and "TOOT." "Maam" is only vertically symmetrical if it is spelled with capital letters, but depending on the font, "otto" and "toot" can be vertically symmetrical if spelled with lower case letters as well.
Certain fonts or cursive writing can render many normally symmetrical letters asymmetrical. Even O is asymmetrical when written in cursive.
When written in capital letters, the word "SWIMS" is one of the English language's only words with rotational symmetry. Rotational symmetry is when an object maintains its shape even after being rotated. When rotated 180 degrees, "SWIMS" still looks like "SWIMS."
In certain fonts, the lowercase letters a, c and l are horizontally symmetrical, the lowercase letters u, v and w are vertically symmetrical, and the lowercase letter o is infinitely symmetrical.