Another way to define knot equivalence is that two knots are equivalent when there is a continuous family of homeomorphisms formula_9 of space onto itself, such that the last one of them carries the first knot onto the second knot. (More formally: Two knots formula_10 and formula_11 are equivalent if there exists a continuous mapping formula_12 such that a) for each formula_13 the mapping taking formula_14 to formula_15 is a homeomorphism of formula_16 onto itself; b) formula_17 for all formula_14; and c) formula_19. Such a function formula_20 is known as an ambient isotopy.)