In knot theory there are several competing notions of the quantity writhe or Wr{\displaystyle \operatorname {Wr} }. In one sense it is purely a property of an oriented link diagram and assumes integer values. In another sense it is a quantity that describes the amount of "coiling" of a mathematical knot (or any closed simple curve) in three-dimensional space and assumes real numbers as values. In both cases writhe is a geometric quantity meaning that while deforming a curve (or diagram) in such a way that does not change its topology one may still change its writhe.