Aperiodic
Somebody posted a smart-ass comment asking how I felt about the existence of the word “aperiodic,” which is how nonrepeating behavior is usually described. I managed to delete the comment accidentally. The person was a slashdotter because they prefaced the coment with [-1: Offtopic]. Anyway – it’s a legitimate question. Here’s the answer: I obviously know that the correct word is aperiodic. However, the term “Nonperiodic Central Trajectory” was coined by Edward Lorenz in the landmark 1963 paper Deterministic Nonperiodic Flow. This paper established the famous Lorenz Attractor and became one of the cornerstones of what is now called “chaos theory.” I think Lorenz used the word “nonperiodic” rather than “aperiodic” because the whole point is that it is almost periodic – the trajectory stays within a certain range of possible values (hence “central”) and makes loops that feel periodic, even though they are not.