NotebookOpen["name"] opens an existing notebook with the specified name, returning the corresponding notebook object. NotebookOpen["name", options] opens a notebook using the ...

! expr is the logical NOT function. It gives False if expr is True, and True if it is False.

Orderless is an attribute that can be assigned to a symbol f to indicate that the elements e_i in expressions of the form f[e_1, e_2, ...] should automatically be sorted into ...

expr /. rules applies a rule or list of rules in an attempt to transform each subpart of an expression expr.

ReplaceList[expr, rules] attempts to transform the entire expression expr by applying a rule or list of rules in all possible ways, and returns a list of the results ...

RotateLeft[expr, n] cycles the elements in expr n positions to the left. RotateLeft[expr] cycles one position to the left. RotateLeft[expr, {n_1, n_2, ...}] cycles elements ...

lhs -> rhs or lhs -> rhs represents a rule that transforms lhs to rhs.

StatusArea[expr, string] displays string in the status area of the current notebook when the mouse pointer is in the region where expr appears.

StringLength["string"] gives the number of characters in a string.

x_y^z is the low-level box representation for x_y^z in notebook expressions.