Link

There are several different definition of link.

In knot theory, a link is one or more disjointly embedded circles in three-space. More informally, a link is an assembly of knots with mutual entanglements. Kuperberg (1994) has shown that a nontrivial knot or link in  has four collinear points (Eppstein). Like knots, links can be decomposed into basic units known as prime links.

The term "link" is also used primarily by physicists to refer to a graph edge.

REFERENCES:

Bar-Natan, D. "The Hoste-Thistlethwaite Link Table." https://www.math.toronto.edu/~drorbn/KAtlas/Links/.

Cerf, C. "Atlas of Oriented Knots and Links." Topology Atlas Invited Contributions 3, No. 2, 1-32, 1998. https://at.yorku.ca/t/a/i/c/31.htm.

Doll, H. and Hoste, J. "A Tabulation of Oriented Links." Math. Comput. 57, 747-761, 1991.

Eppstein, D. "Colinear Points on Knots." https://www.ics.uci.edu/~eppstein/junkyard/knot-colinear.html.

Kuperberg, G. "Quadrisecants of Knots and Links." J. Knot Theory Ramifications 3, 41-50, 1994.