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Once, when my daughter first came across the word “chaos” in her readings, she asked me what it meant. I am not quite sure why she knew that I would be able to explain that word, but she must have sensed that there was a mathematical meaning to this new word she had encountered. I explained that in that context, it meant things happening that could not be predicted. However, I added (as she rolled her eyes), things that we call “chaotic” are often very able to be predicted. For example, the movement of a leaf in a stream is often described as “chaotic”, but, if we look hard enough, there are definite equations that would define such motion. A similar idea relates to the word “random.” While we often refer to “random” as unable to be anticipated, random variables are often very able to be predicted. For example, if we flip a coin 100 times, we would expect it to come up heads about fifty times. Once we know a probability distribution, “random” does not mean unpredictable at all. I found myself thinking of this recently when I encountered a former student while out with my family, an encounter that might best be described as “random.”