An isolated point of a graph is a node of degree 0 (Hartsfield and Ringel 1990, p. 8; Harary 1994, p. 15; D'Angelo
and West 2000, p. 212; West 2000, p. 22). The number of  -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 on a curve is more commonly known as an acnode.
An isolated point of a discrete set  is a member of  (Krantz 1999, p. 63).
D'Angelo, J. P. and West, D. B. Mathematical Thinking: Problem-Solving and Proofs, 2nd ed.
Upper Saddle River, NJ: Prentice-Hall, 2000.
Harary, F. Graph Theory. Reading, MA: Addison-Wesley, 1994.
Hartsfield, N. and Ringel, G. Pearls in Graph Theory: A Comprehensive Introduction. San
Diego, CA: Academic Press, 1990.
Krantz, S. G. "Discrete Sets and Isolated Points." §4.6.2 in Handbook of Complex Variables. Boston, MA: Birkhäuser,
pp. 63-64, 1999.
Sloane, N. J. A. Sequence A002494/M1762 in "The On-Line Encyclopedia of Integer
Sequences."
West, D. B. Introduction to Graph Theory, 2nd ed. Englewood Cliffs,
NJ: Prentice-Hall, 2000.
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