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In mathematics two links $L_0 \subset S^n$ and $L_1 \subset S^n$ are concordant if there is an embedding $f : L_0 \times \left(\right) \to S^n \times \left(\right)$ such that $f\left(L_0 \times \\right) = L_0 \times \$ and $f\left(L_0 \times \\right) = L_1 \times \$.
By its nature, link concordance is an equivalence relation. It is weaker than isotopy, and stronger than homotopy: isotopy implies concordance implies homotopy. A link is a slice link if it is concordant to the unlink.
== Concordance invariants ==
A function of a link that is invariant under concordance is called a concordance invariants.
The linking number of any two components of a link is one of the most elementary concordance invariants. The signature of a knot is also a concordance invariant. A subtler concordance invariant are the Milnor invariants, and in fact all rational finite type concordance invariants are Milnor invariants and their products, though non-finite type concordance invariants exist.