MultilaunchWarning is a global option that specifies whether a warning is given when you try to modify user preferences while running two copies of Mathematica simultaneously.

Needs["context`"] loads an appropriate file if the specified context is not already in $Packages. Needs["context`", " file"] loads file if the specified context is not ...

NominalVariables is an option for fitting functions such as LinearModelFit that specifies which variables should be treated as having discrete values specified by names.

NotebookClose[notebook] closes the notebook corresponding to the specified notebook object. NotebookClose[] closes the current evaluation notebook.

NotebookDelete[notebook] deletes the current selection in the notebook corresponding to the specified notebook object. NotebookDelete[] deletes the current selection in the ...

Notebooks[] gives a list of notebooks currently open in the front end.

NRoots[lhs == rhs, var] yields a disjunction of equations which represent numerical approximations to the roots of a polynomial equation.

Null is a symbol used to indicate the absence of an expression or a result. It is not displayed in ordinary output. When Null appears as a complete output expression, no ...

NumberPadding is an option for NumberForm and related functions which gives strings to use as padding on the left- and right-hand sides of numbers.

OptionInspectorSettings -> {opt_1 -> val_1, opt_2 -> val_2, ...} is a global option that specifies the display of options in the Option Inspector.