FileExtension["file"] gives the file extension for a file name.
FileNameSplit["filename"] splits a file name into a list of parts.
FindPermutation[expr] gives a permutation that produces expr by permuting Sort[expr].FindPermutation[expr 1, expr 2] gives a permutation that converts expr_1 to expr_2 for ...
FractionBox[x, y] is a low-level formatting construct that represents x/y in notebook expressions.
Front
(Built-in Mathematica Symbol) Front is a symbol that represents the front of a graphic for purposes of placement and alignment.
GeodesicErosion[marker, mask] gives the fixed point of the geodesic erosion of the image marker constrained by the image mask.
GroupActionBase is an option to specify a base for a group.
GroupGenerators[group] returns a list of generators of group.
x++ increases the value of x by 1, returning the old value of x.
IntegerQ[expr] gives True if expr is an integer, and False otherwise.