A multi-knot is multiple edit points at the same location in space.

CV multiplicity is multiple CVs at the same location in space.

Multi-knots and CV Multiplicity achieve similar effects (sharper bends in curves), even though they are different mathematically.

Multi-knots are usually the result of curve or surface editing operations that require a sharp turn in a curve.

Multi-knots and CV multiplicity are generally undesirable. Some tools cannot work with them, they do not build very good surfaces or animate predictably, and some other software packages will not accept models with multi-knots.