isolated vertex

An isolated point of a graph is a node of degree 0. The number of n-node graphs with no isolated points are 0, 1, 2, 7, 23, 122, 888, ... (OEIS A002494), the first few of which are illustrated above. The number of graphical partitions of length n is equal to the number of n-node graphs that have no isolated points. Connected graphs have no isolated points. An isolated point on a curve is more commonly known as an acnode. An isolated point of a discrete set S is a member of S.

acnode | endpoint | graphical partition | neighborhood