A knot invariant in the form of a Polynomial such as the Alexander Polynomial, BLM/Ho Polynomial, Bracket Polynomial, Conway Polynomial, Jones Polynomial, Kauffman Polynomial F, Kauffman Polynomial X, and Vassiliev Polynomial.
References
Lickorish, W. B. R. and Millett, K. C. ``The New Polynomial Invariants of Knots and Links.'' Math. Mag. 61, 3-23, 1988.