Sciency Words: Stochastic

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


At first glance, stochastic appears to have a pretty easy definition. Basically, it means random. A stochastic event can be defined, quite simply, as a random event. So why do scientists need this weird term? Why can’t they just say random if they mean random?

I’ve seen this word now in a surprisingly wide range of scientific fields, most recently in relation to the population dynamics of endangered species and then in relation to the magnetic field of Jupiter. The thing is that in actual usage, stochastic and random aren’t quite synonyms. A better definition for stochastic might be “seemingly random.”

The word originates from a Greek word meaning “to aim at” or “to shoot at.” So it’s an archery term, but the Greeks also used it to mean “to guess at.” I like this linguistic metaphor because a guess really is like aiming for the truth; whether or not you hit the mark is another matter.

Anyway, the word seems to have migrated from Greek to German to English, and in its modern scientific sense it refers to something that might be predictable in theory but appears to be random in practice. As an example, you may have heard that the flapping of a butterfly’s wings could set in motion a chain of events ultimately leading to a devastating hurricane.

In theory, these butterfly-initiated hurricanes could be predicted, if only we knew the exact locations and flapping behaviors of every single butterfly on Earth (along with a million and one other factors). But in practice, since we can’t gather all the necessary data, we can only make educated guesses about when and where the next hurricane will hit.

In other words, hurricanes are stochastic events. They seem random, even though they’re not.

12 thoughts on “Sciency Words: Stochastic

  1. Interesting etymology.

    The problem I see with the distinction between stochastic and random is that it relegates the word “random” to quantum events. But I’m personally fine using “random” to refer to things like the results of a dice throw, even if the result wouldn’t be random for Laplace’s demon.

    That said, it’s nice to know that “stochastic” essentially means “random.” Thanks!

    Liked by 2 people

    1. So I did check to see if this word is used in quantum physics. It is. There’s something called quantum stochastic calculus, which involved a lot of very intimidating-looking math. I figured it would be best for me to leave that out of this post, since I really didn’t understand what I was looking at.

      Liked by 2 people

      1. I read a science communication guideline once which advised that math of just about any kind was problematic in writing for the general public. Since math has never been my strong point (I generally ignore the math in whatever science papers I do read, hoping I can get by without parsing it), it’s never been a stricture that I’ve chafed at.

        Liked by 1 person

  2. hee hee. A friend and I have noticed we use the word ‘random’ too often when we’re together. We’re always trying to find silly alternatives. I’m looking forward to trying out stochastic. Appropriately, of course.

    Liked by 1 person

    1. Excellent! I kind of want to start correcting people whenever they say something is random and explaining that it’s actually stochastic. I’m pretty sure I’ll get beaten up for being a nerd, but whatever. It’ll be worth it!

      Liked by 1 person

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