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.

Most[expr] gives expr with the last element removed.

MultilineFunction is an option for UnderscriptBox and related box objects that specifies what to do when the contents of a box object are too long to fit on one line.

NonConstants is an option for D which gives a list of objects to be taken to depend implicitly on the differentiation variables.

NotebookInformation[] gives a list of properties of the current evaluation notebook.NotebookInformation[notebook] gives a list of properties for the specified notebook.

% n or Out[n] is a global object that is assigned to be the value produced on the n\[Null]^th output line. % gives the last result generated. %% gives the result before last. ...

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

PassEventsUp is an option to EventHandler that specifies whether events handled by a particular event handler should be passed up to event handlers in outer expressions.

PrincipalValue is an option for Integrate that specifies whether the Cauchy principal value should be found for a definite integral.

PrivatePaths -> {opt_1 -> val_1, opt_2 -> val_2, ...} is a global option that specifies settings for paths private to the notebook front end.