Denominator[expr] gives the denominator of expr.
DialogNotebook[{cell_1, cell_2, ...}] represents a dialog notebook that can be manipulated by the Mathematica front end.
Dimensions[expr] gives a list of the dimensions of expr. Dimensions[expr, n] gives a list of the dimensions of expr down to level n.
FindVertexCover[g] finds a vertex cover of the graph g with a minimum number of vertices.
LineGraph[g] gives the line graph of the graph g.
Modulus
(Built-in Mathematica Symbol) Modulus -> n is an option that can be given in certain algebraic functions to specify that integers should be treated modulo n.
MovingMedian[list, r] gives the moving median of list, computed using spans of r elements.
NotebookConvertSettings -> {opt_1 -> val_1, opt_2 -> val_2, ...} is a global option that specifies settings for converting imported legacy notebooks.
Numerator[expr] gives the numerator of expr.
Primes
(Built-in Mathematica Symbol) Primes represents the domain of prime numbers, as in x \[Element] Primes.