Remove
(Built-in Mathematica Symbol) Remove[symbol_1, ...] removes symbols completely, so that their names are no longer recognized by Mathematica. Remove["form_1", "form_2", ...] removes all symbols whose names ...
RenameFile["file_1", "file_2"] renames file_1 to file_2.
SameTest is an option whose setting gives a pairwise comparison function to determine whether expressions should be considered the same.
SelectionMove[obj, dir, unit] moves the current selection in an open notebook in the front end in the direction dir by the specified unit. SelectionMove[obj, dir, unit, n] ...
SetAccuracy[expr, a] yields a version of expr in which all numbers have been set to have accuracy a.
SetterBar[x, {val_1, val_2, ...}] represents a setter bar with setting x and with setter buttons for values val_i.SetterBar[Dynamic[x], {val_1, val_2, ...}] takes the setting ...
ShowContents is an option for selections that specifies whether an object represented by a StyleBox should be displayed on the screen or replaced by blank space.
ShowSpecialCharacters is an option for Style and Cell that specifies whether to replace \[Name], \:nnnn, etc. by explicit special characters.
SpanAdjustments is an option for selections that specifies the height and width of spanning characters.
Streams
(Built-in Mathematica Symbol) Streams[] gives a list of all streams that are currently open. Streams["name"] lists only streams with the specified name.