FactorInteger[n] gives a list of the prime factors of the integer n, together with their exponents. FactorInteger[n, k] does partial factorization, pulling out at most k ...
FileFormat["name"] attempts to determine what Import format could be used to import the file corresponding to " name".
Filling
(Built-in Mathematica Symbol) Filling is an option for ListPlot, Plot, Plot3D, and related functions that specifies what filling to add under points, curves, and surfaces.
FindDistributionParameters[data, dist] finds the parameter estimates for the distribution dist from data.FindDistributionParameters[data, dist, {{p, p_0}, {q, q_0}, ...}] ...
FontVariations is an option for Style, Cell, and related constructs that specifies what font variations should be used.
FrameBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for cells that specifies default settings.
Frame
(Built-in Mathematica Symbol) Frame is an option for Graphics, Grid, and other constructs that specifies whether to include a frame.
FromCharacterCode[n] gives a string consisting of the character with integer code n. FromCharacterCode[{n_1, n_2, ...}] gives a string consisting of the sequence of ...
General
(Built-in Mathematica Symbol) General is a symbol to which general system messages are attached.
GenericCylindricalDecomposition[ineqs, {x_1, x_2, ...}] finds the full-dimensional part of the decomposition of the region represented by the inequalities ineqs into ...