Invisible[expr] displays as space that is the same size as the formatted version of expr.

Joined is an option for ListPlot and related functions that specifies whether points in each dataset should be joined into a line, or should be plotted as separate points.

LinkLaunch["prog"] starts the external program prog and opens a MathLink connection to it.

LinkPatterns[link] gives a list of the patterns for which definitions were set up when the external program associated with the specified MathLink connection was installed.

Links[] gives a list of all MathLink connections that are currently open. Links[patt] lists only links whose names match the specified string pattern.

MaxStepFraction is an option to functions like NDSolve that specifies the maximum fraction of the total range to cover in a single step.

MeanFilter[image, r] filters image by replacing every value by the mean value in its range r neighborhood. MeanFilter[data, r] applies mean filtering to an array of data.

NormalsFunction is an option for Plot3D and related functions that specifies a function to apply to determine the effective surface normals at every point.

NotebookSelection[] represents the current selection in the current evaluation notebook in the front end.NotebookSelection[nb] represents the current selection associated ...

OddQ[expr] gives True if expr is an odd integer, and False otherwise.