SUP is for superscripts
sup
The "sup" element is for treating a character as a superscript, displaying it in a smaller text than its surrounding text, and raising its typographic baseline.
Examples
area A = π r2 A = π r<<sup 2>>
sum ∑ = x0 + x1 + x2 + ... ∑ = x<<sup 0>> + x<<sup 1>> + x<<sup 2>> + ...
ordinals 1st, 2nd, 3rd, 4th 1<<sup st>>, 2<<sup nd>>, 3<<sup rd>>, 4<<sup th>>
one-fifth 1/5 <<sup 1>>/<<sub 5>>