StringToStream["string"] opens an input stream for reading from a string.
Stub
(Built-in Mathematica Symbol) Stub is an attribute which specifies that if a symbol is ever used, Needs should automatically be called on the context of the symbol.
StyleBoxAutoDelete is an option for selections that specifies whether a StyleBox wrapped around them should be automatically removed when the expression is edited.
StyleMenuListing is an option for cells that specifies whether a given cell style is listed in the Format \[FilledRightTriangle] Style submenu.
SubscriptBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for selections that specifies settings for SubscriptBox objects.
SubsetEqual[x, y, ...] displays as x \[SubsetEqual] y \[SubsetEqual] ....
Subset
(Built-in Mathematica Symbol) Subset[x, y, ...] displays as x \[Subset] y \[Subset] ....
SubStar
(Built-in Mathematica Symbol) SubStar[expr] displays as expr_*.
SubsuperscriptBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for selections that specifies settings for SubsuperscriptBox objects.
SuchThat[x, y] displays as x \[SuchThat] y.