Chreo...what?

Because of where my interests have led me, I am often asked to explain the word "chreostochastic". Here is a quick attempt to which I can direct future requests.

"Stochastic" describes a process where chance decides the outcome of an event within limits set by the preceding event. Imagine that you close your eyes, spin round on the spot, and then jump. Your landing point will be, let's say, somewhere within a metre of your starting place. Keep your eyes shut, spin again, jump again. Which way you jump each time is roughly random; how far you can jump is limited by your own strength and balance; and where the jump of a given strength and direction will take you is decided by where the last jump left you. That last fact makes this process of jumping a stochastic one. (Mathematicians call your series of jumps a "random walk".)

"Chreodic" means "channelled". Imagine that your bizarre series of spinning jumps with closed eyes, your random walk, takes place within a grassy furrow whose sides slope gently upward to either side of you - perhaps to a height of three or four metres, at an angle of thirty degrees or so. Beyond the slopes lie other, parallel furrows. Your series of jumps may, in theory, take you up one of the slopes and over the top into the next furrow - but gravity ensures that, once on a slope, you are more likely to jump down than up, and so more likely to stay in the furrow than to leave it. Your random walk is being channelled – it is chreodic. If you ever do move over the top into the next furrow, the same reasoning is most likely to keep you there rather than returning.

Combining the two ... a chreostochastic process is one in which each step is probabilistic, but from a starting point decided by the previous step, but within partial constraints which cause it to tend in one direction without actually preventing other outcomes.