U-duality
symmetry of M-theory compactifications that includes T-duality and S-duality as subgroups; the supergravity theory U-duality group is an E-series Lie group, while stringy effects break it to a discrete subgroup
S-duality
equivalence of two physical theories under which the coupling constant of one is the inverse of the other
T-duality
duality in string theory in which compactifications on small spaces are equivalent to compactications on spaces of the inverse size; interchanges discrete KK momentum with winding number