InfixNotation[op, func] forces the box structure op to be treated as an infix operator representing the function func in input and output.

Notation[boxes \[DoubleLongLeftRightArrow] expr] parses any input box structure boxes internally as expr, and formats any expression matching expr as boxes in ...

ParsedBoxWrapper is a wrapper that wraps parsed boxes which come from the TagBox expressions that are embedded in Notation, Symbolize and InfixNotation statements.

Symbolize[boxes] forces any box structure matching boxes to be treated internally as a single symbol anywhere it appears in an input expression.

Due to the complex inner workings of the Notation Package it is helpful to outline some of the more advanced features and structures of the Mathematica front end and how they ...

ButcherOrder[tree] gives the number of vertices in tree.

ButcherPlotColumns is an option to ButcherPlot that specifies the number of columns in the array of Butcher tree plots.

ButcherPlotNodeSize is an option to ButcherPlot that specifies a scaling factor for the nodes of the trees in the plot.

AgeOfUniverse is the age of the universe, a physical constant.

BohrRadius is the Bohr radius, an atomic constant.