Editing Genus (mathematics) (section)

===Knot===
The '''[[genus of a knot|genus]]''' of a [[knot (mathematics)|knot]] ''K'' is defined as the minimal genus of all [[Seifert surface]]s for ''K''.<ref>{{Citation|first=Colin |last= Adams|author-link=Colin Adams (mathematician)|title=The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots |publisher=[[American Mathematical Society]]|year=2004|isbn=978-0-8218-3678-1}}</ref> A Seifert surface of a knot is however a [[manifold with boundary]], the boundary being the knot, i.e.
[[Homeomorphism|homeomorphic]] to the [[unit circle]]. The genus of such a surface is defined to be the genus of the two-manifold, which is obtained by gluing the unit disk along the boundary.