An isolated point on a curve, also known as an acnode or hermit point, is a point which has no other points in its neighborhood.

An isolated point of a graph is a node of degree 1 (Harary 1994, p. 15). The number of n-node graphs with no isolated points are 0, 1, 2, 7, 23, 122, 888, ... (Sloane's A002494), the first few of which are illustrated above.

An isolated point of a discrete set S is a member of S (Krantz 1999, p. 63).