How many parts interact, and how tangled their interaction is. Complexity is not difficulty; it is the number of ways to be wrong.

Changing in response to conditions rather than fixed in advance. Of a thing decided at the moment rather than beforehand.

A point where many connections bind together. From the Latin for binding — a nexus is a knot rather than a place.

A curve that circles while moving outward or in, never closing. A spiral returns to the same angle at a different depth.