Knots are closed curves.
In 3D the simplest knot is the circle aka the 1-sphere. In ND the simplest knot is the (N-2)-sphere. This is more obvious if you think of the (N-2)-sphere as the (N-2)-ring.
To make an overhand/trefoil knot you cut the ring, wrap one of the loose ends around the other end, then reattach the two ends. This can be done in any number of dimensions.
Question: If N is even, are there two distinct trefoil knots? That is, is the trefoil knot orientable?
Question: is the 4D torus a knot?