# writhe

The writhe of a link, also called its twist number, is the sum of the signs of the link’s crossings. In short, it is the sum of the positive crossings minus the sum of the negative crossings. Note that the writhe is not an isotopy invariant and that is actually depends on the regular homotopy class of its projection.

Title writhe Writhe 2013-03-22 16:29:22 2013-03-22 16:29:22 PrimeFan (13766) PrimeFan (13766) 6 PrimeFan (13766) Definition msc 57M25 twist number