A fastening made by tying rope, cord, or thread.

• A particular way of tying that creates a looped fastening.

A tangle or hard clump in hair, thread, or fibers.

A hard lump in wood where a branch grew; a wood knot.

• A small swelling or tight spot in tissue or muscle.

A unit of speed equal to one nautical mile per hour.

A difficult problem, complication, or crux of a matter.

To tie or fasten with a knot or knots.

• To wrinkle or contract, as the brow.

A closed non-self-intersecting curve studied in topology.