Abstract
Let f be a map from V (G) to {0, 1, ..., k - 1} where k is an integer, 1 <= k <= vertical bar V (G)vertical bar|. For each edge uv assign the label f(u)f(v)(mod k). f is called a k-product cordial labeling if vertical bar v(f) (i) - v(f) (j)vertical bar <= 1, and vertical bar e(f) (i) - e(f) (j)vertical bar <= 1, i, j is an element of {0, 1, ..., k - 1}, where v(f) (x) and e(f) (x) denote the number of vertices and edges respectively labeled with x (x = 0, 1, ..., k - 1). In this paper, we investigate the k-product cordial behaviour of union of graphs.