StructuredSelection is an option for Cell that specifies whether to allow only complete subexpressions in the cell to be selected interactively using the front end.
StruveL
(Built-in Mathematica Symbol) StruveL[n, z] gives the modified Struve function L n (z).
SystemHelpPath is a global option that specifies which directories are searched for the help notebooks used within the help system.
TabSpacings is an option for character selections that specifies the number of spaces in ems that the cursor advances when the Tab key is pressed.
ThompsonGroupTh[] represents the sporadic simple Thompson group Th.
Underlined represents an underlined font.
UndirectedGraph[g] gives an undirected graph from the directed graph g.
VertexSize is an option and property for Graph and related functions that specifies the size used for vertices.
White
(Built-in Mathematica Symbol) White represents the color white in graphics or style specifications.
Whitespace represents a sequence of whitespace characters in StringExpression.