The exterior of a knot 
is the complement of an open solid torus knotted like 
. The removed open solid torus
is called a tubular neighborhood (Adams 1994,
p. 258).
Knot Exterior
See also
Knot Complement, Gordon-Luecke Theorem, Tubular NeighborhoodExplore with Wolfram|Alpha
References
Adams, C. C. The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots. New York: W. H. Freeman, 1994.Referenced on Wolfram|Alpha
Knot ExteriorCite this as:
Weisstein, Eric W. "Knot Exterior." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/KnotExterior.html