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  "body": "\n## Summary\n\nA Seifert surface of a [[knot|QYEAZTYGPT]] or [[link|1A5WRCNTM3]] is a compact, connected, orientable surface in space whose boundary is the knot or link.\nEvery oriented link has one, by an algorithm of Herbert Seifert from 1934.\nThe least [[genus|NJ787GZS1N]] of a Seifert surface of a knot is the genus of the knot, a [[knot invariant|GZQ5ZE3X6G]].\nSeifert surfaces are also used to define the Alexander polynomial and the signature of a knot.\n\n## Explanations\n\n### L1 human\n\nDip a knotted wire loop into soap solution: the soap film that forms is a surface whose edge is the knot.\nA Seifert surface is such a surface with two distinct sides, so that it can be painted in two colours.\nFor a round circle, a flat disk works.\nFor more complicated knots, the surface needs handles, and the least number of handles needed is the genus of the knot.\n",
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