In knot theory, a branch of mathematics, a knot or link ${\displaystyle K}$ in the 3-dimensional sphere ${\displaystyle S^{3}}$ is called fibered or fibred (sometimes Neuwirth knot in older texts, after Lee Neuwirth) if there is a 1-parameter family ${\displaystyle F_{t}}$ of Seifert surfaces for ${\displaystyle K}$, where the parameter ${\displaystyle t}$ runs through the points of the unit circle ${\displaystyle S^{1}}$, such that if ${\displaystyle s}$ is not equal to ${\displaystyle t}$ then the intersection of ${\displaystyle F_{s}}$ and ${\displaystyle F_{t}}$ is exactly ${\displaystyle K}$.