MessageList[n] is a global object assigned to be a list of the names of messages generated during the processing of the n\[Null]^th input line.

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

NumberMarks is an option for InputForm and related functions that specifies whether ` marks should be included in the printed forms of approximate numbers.

NumberSigns is an option for NumberForm and related functions which gives strings to use as signs for negative and positive numbers.

PackingMethod is an option for GraphPlot and related functions which specifies how disconnected components should be packed together in the layout produced.

PerformanceGoal is an option for plotting and various other algorithmic functions that specifies what aspect of performance to try to optimize with Automatic settings for ...

PlotLayout is an option used by WaveletListPlot and similar functions to specify the layout of multiple plots.

PlotPoints is an option for plotting functions that specifies how many initial sample points to use.

PlotRegion is an option for graphics functions that specifies what region of the final display area a plot should fill.

RandomChoice[{e_1, e_2, ...}] gives a pseudorandom choice of one of the e_i. RandomChoice[list, n] gives a list of n pseudorandom choices. RandomChoice[list, {n_1, n_2, ...}] ...