Therefore[x, y] displays as x \[Therefore] y.
ThompsonGroupTh[] represents the sporadic simple Thompson group Th.
TildeEqual[x, y, ...] displays as x \[TildeEqual] y \[TildeEqual] ....
TildeFullEqual[x, y, ...] displays as x \[TildeFullEqual] y \[TildeFullEqual] ....
Tilde
(Built-in Mathematica Symbol) Tilde[x, y, ...] displays as x \[Tilde] y \[Tilde] ....
TildeTilde[x, y, ...] displays as x \[TildeTilde] y \[TildeTilde] ....
TitsGroupT[] represents the simple Tits group T.
UnionPlus[x, y, ...] displays as x \[UnionPlus] y \[UnionPlus] ....
UnsavedVariables is an option for Manipulate, DynamicModule, and related functions that specifies local symbols that should not be saved when the notebook containing them is ...
UpArrowBar[x, y, ...] displays as x\[UpArrowBar]y\[UpArrowBar]....