The unlink, also called the trivial link, of 
components consist of 
disjoint circles in a plane (Rolfsen 1976, p. 65).
Unlink
See also
Link, UnknotExplore with Wolfram|Alpha
References
Adams, C. C. The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots. New York: W. H. Freeman, p. 18, 1994.Livingston, C. Knot Theory. Washington, DC: Math. Assoc. Amer., p. 16, 1993.Rolfsen, D. Knots and Links. Wilmington, DE: Publish or Perish Press, 1976.Referenced on Wolfram|Alpha
UnlinkCite this as:
Weisstein, Eric W. "Unlink." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Unlink.html