As I have voiced in slightly different words before, as I got closer and closer to the looking glass of being pedantic I found myself falling through into a world where nothing quite makes sense and "technically correct" is no longer the best kind of correct. I'm writing about this again because of two examples that came up for me recently, both having to do, naturally, with cephalopods.
I have discussed many, many times the difference between "tentacle" and "arm" as it pertains to cephalopods. On a squid it's somewhat straightforward: tentacles are longer and have suction discs only on the clubs at the ends while arms are shorter and have suction discs all the way down. However there are some problems with this. First when you look outside the cephalopods this distinction no longer makes any sense. Snails, polychaete worms, star-nosed moles all have tentacles. They are often chemosensory but not always, they are often used for grabbing or holding food but not always. Generally the only other appendage that gets called an "arm" are human arms. So these are not definitions (which in science, technical words are generally thought to have definitions) but rather conventions. That is, it is convention to call a cephalopod appendage with suction discs only on the club at the end a tentacle but this is not the definition of the word "tentacle."
The other real problem with arm vs. tentacle within the cephalopods is that the nautilidae have "tentacles" but lack suction discs entirely. So again, these terms, both "arm" and "tentacle" appear to be conventions and not definitions. That's fine, we use language in this way in colloquial life all the time. It generally leads to only minor confusion. The thing is that in science, we have tricked ourselves into believing that the words we use always have a very precise meaning. The truth is, this is only sometimes true. Planet, continent, species are all examples of very common terms that really lack a precise definition. But there's fun to be had here. The natural world is tenaciously difficult to put into the boxes our human brains want to put it in. The fun is figuring out what other sorts of containers we can use. Turns out these imperfect conventions are fairly useful.
The other example around technical language that came up recently was around the word "octopi." In a lot of the scientific community this is regarded as an "incorrect" plural of "octopus." This is because the word "octopus"is a Greek route word and not a Latin route word and the -us to -i pluralization is not used in Greek. So the "technically" correct pluralization of "octopus" is "octopuses." But here's the rub: a lot of people use the word "octopi."
And this is the argument that I think we all, myself included, need to do better at remembering: if people use a word and you understand it, it probably means it's a word. If we only obey the "dictionary definitions" of words or the "technical" definitions of words we're saying that a whole section of language is completely off limits: slang. Even though it might not be "good grammar" you know perfectly well what I mean when I use the words "a'int," "dope," "cool" (I don't mean temperature), etc.
This might be where we all fall into the looking glass of pedantry and "technically" correct: I'll introduce the character of the Merriam-Webster dictionary. They include "octopi" among their plurals for "octopus." So does this mean that "if the dictionary says it's a word, it's a word"? Kind of. Dictionaries change, words change, usage change and with this example that's the real point. A lot of us think about the dictionary as being some kind of Platonic codification of our language. Sorry, though, language refuses to play that game. So if you understand when someone says "octopi" that they mean "more than one octopus" why correct them?
These rules morph and flex depending on your audience. Should I use "octopuses" when I'm addressing marine biologists and "octopi" if my eight year old student has just used that word and not "octopuses?" Yeah probably yes to both of those.
As I was developing this post I came across this graph on Twitter and thought about not even writing this post at all. As you can see, I did write the post but I wanted to include it here, because, well, I still think it sums up what I just said a bit better than I said it.
click to embiggen. Courtesy @robdrummond
As usual I'll invite you to disagree, yell, berate and complain in the comments.