SphericalHarmonicY[l, m, \[Theta], \[Phi]] gives the spherical harmonic Y_l^m(\[Theta], \[Phi]).
StirlingS1[n, m] gives the Stirling number of the first kind S_n^(m).
StreamPoints is an option to StreamPlot, ListStreamPlot, and related functions that determines how many streamlines to draw.
StringInsert["string", " snew", n] yields a string with " snew" inserted starting at position n in " string". StringInsert["string", " snew", -n] inserts at position n from ...
StringTake["string", n] gives a string containing the first n characters in " string". StringTake["string", -n] gives the last n characters in " string". StringTake["string", ...
StyleBox[boxes, options] is a low-level representation of boxes to be shown with the specified option settings. StyleBox[boxes, " style"] uses the option setting for the ...
TagBox
(Built-in Mathematica Symbol) TagBox[boxes, tag] is a low-level box construct that displays as boxes but maintains tag to guide the interpretation of boxes on input.
ToExpression[input] gives the expression obtained by interpreting strings or boxes as Mathematica input. ToExpression[input, form] uses interpretation rules corresponding to ...
TrigToExp[expr] converts trigonometric functions in expr to exponentials.
UnitBox
(Built-in Mathematica Symbol) UnitBox[x] represents the unit box function, equal to 1 for |x| <= 1/2 and 0 otherwise.UnitBox[x_1, x_2, ...] represents the multidimensional unit box function, equal to 1 if ...