Degrees[g] returns the degrees of vertex 1, 2, 3, ... in that order.

DegreesOf2Neighborhood[g, v] returns the sorted list of degrees of vertices of graph g within a distance of 2 from v.

DeleteFromTableau[t, r] deletes the last element of row r from Young tableau t.

DeleteVertex[g, v] deletes a single vertex v from graph g. Here v is a vertex number.

DeleteVertices[g, vList] deletes vertices in vList from graph g. vList has the form {i, j, ...}, where i, j, ... are vertex numbers.

DerangementQ[p] tests whether permutation p is a derangement, that is, a permutation without a fixed point.

Diameter[g] gives the diameter of graph g, the maximum length, among all pairs of vertices in g, of a shortest path between each pair.

DihedralGroupIndex[n, x] returns the cycle index of the dihedral group on n symbols, expressed as a polynomial in x[1], x[2], ..., x[n].

DihedralGroup[n] returns the dihedral group on n symbols. Note that the order of this group is 2 n.

Dihedral is an argument to the Polya-theoretic functions ListNecklaces, NumberOfNecklaces, and NecklacePolynomial, which count or enumerate distinct necklaces. Dihedral ...