“…In other words, the vertices in the dominating set S can be partitioned into 2-sets such that if {u, v} is a 2-set, then uv ∈ E(G) or the distance between u and v is 2. We say that u and v are paired, and that u and v are partners with respect to the resulting semi-matching consisting of the pairings of vertices of S. The semipaired domination number, denoted by γ pr2 (G), is the minimum cardinality of a semi-PD-set of G. We call a semi-PD-set of G of cardinality γ pr2 (G) a γ pr2 -set of G. Semipaired domination was introduced in [11] and studied, for example, in [12,13,[19][20][21]. From the definitions, we observe the following.…”