Magnification is an option for Style and Cell that specifies what magnification to use for display.
MakeExpression[boxes, form] is the low-level function used in Mathematica sessions to construct expressions from boxes.
MantissaExponent[x] gives a list containing the mantissa and exponent of a number x. MantissaExponent[x, b] gives the base-b mantissa and exponent of x.
MaxSteps is an option to functions like NDSolve that specifies the maximum number of steps to take in generating a result.
NHoldFirst is an attribute which specifies that the first argument to a function should not be affected by N.
NormFunction is an option for functions such as FindFit and NDSolve which gives a function to be minimized in generating results.
NotebookFind[notebook, data] sets the current selection in the specified notebook object to be the next occurrence of data. NotebookFind[notebook, data, Previous] sets the ...
NotebookLocate["tag"] locates all cells with the specified tag in your current input notebook, selecting the cells and scrolling to the position of the first one. ...
NumberFieldSignature[a] gives the signature of the field \[DoubleStruckCapitalQ][a] generated by the algebraic number a.
OpenAppend["file"] opens a file to append output to it, and returns an OutputStream object.