A knot, by definition, is an intentional complication in cordage that is either useful or decorative. 

Knots are sorted into categories of hitches, bends, splices, and stoppers.

A knot is a tangled mass of something, like hair.

Knotty, matted, snarled, raveled, twisted, entwined, coiled, unkempt, uncombed, tousled;

A knot is a bump, as in a knot of wood.

A gnarl, knurl, node, lump, knob, swelling, growth, gall, protuberance, bump; 

A knot is an unpleasant feeling of tightness or tension in a part of the body.

"Her stomach was in knots as she unlocked the door.”

A knot is a tightly packed group of people.

A cluster, huddle, bunch, throng, swarm, flock, gang, assemblage, mob, pack.

A knot is a unit of speed especially of ships, aircraft or winds.

A knot is a measure of incremental depth, marked by a series of knots tied at specific lengths along a rope.

You can’t call yourself a sailor if you can’t tie knots. This was the first lesson of junior sailing, just before I started racing, frightened of everything and proficient at nothing.  It became suddenly very clear that knots were the real sets of keys to the boats, knots unlocked the water, knots were the ignition. Knots were the unspoken language of those who went to sea, and I wanted to speak that language so badly. 

I was eight years old and couldn't tie a bowline. I tried to keep it hid. My cover was blown when the 12-year-old skipper sent me forward to tie the sheet to the clew of the jib. It was just me with my back to the crew, alone at middeck with a twisted ravel of cordage in my lap.  I started moving the rope around itself, praying that the bowline would somehow emerge from my desperate tangles, but it was not to be.  After minutes, that felt like hours, one of the senior instructors (he was 14 or so), came forward to help. With a laugh and a snort, he tied the sheet to the jib and never let me forget it. Everybody laughed.

From then on, my fear of not being able to tie knots made them all the more impossible to tie.  I would wrap a mooring line around a cleat, the bowman would walk up behind me, with a dramatic exhale, roll his eyes, and retie it.
Because, it’s not just how to tie knots, it’s when. The cleat hitch to attach a halyard, two half-hitches to secure a fender to the rail, the soft shackle to secure a flapping sail, and, the nemesis bowline for the grommet in the clew.
Eventually, I found the discipline to sit down and learn the knots necessary for sailing, then climbing, and flying (yes, there are knots in flying, too) but my stomach still constricts every time I tie a bowline.

A knot, by definition, is an intentional complication in cordage. My personal history with knots may be complicated, but beyond the tangles, snarls, and bowlines gone wrong, there is an elegance and simplicity to each and every one. Between the sharp end and the bitter end, clarity can be found, and that, to me, is something worth investigating.