I think the last chapter of Because Internet: Understanding the New Rules of Language by Gretchen McCulloch describes beautifully the way we each have our own, personal version of our languages, and what’s captured in the dictionary is more of an aggregate snapshot.
What she doesn’t get into is how many problems it can cause.
One of my really early memories about this is of watching this comedy routine (I’m astonished I was able to find this). Based on the date on that transcript I must have been at least seven or eight years old, and I don’t think I was older than about twelve. Anyway, in it this comedian talks about meeting his college roommate who suggests they split “a pie”, which apparently is not used to mean a pizza where he grew up. I may not call pizza “pie”, but I’ve had enough exposure to that usage that I can interpret it correctly in most contexts. This idea, that regionalisms like this could so confuse people, blew Little Ted’s mind. It really stuck with me.
It’s not just regional variations, though. An example I’m regularly reminded of in daily life are the words “racism” and “racist”.
As a child of the 1990’s and early 2000’s, the common definition I was aware of for “racism” was something along the lines of “people being treated badly because of others’ bigoted views about their race”, and for “racist” something like “a person with bigoted views about racial groups”. In college, around the time I read Racism without Racists by Eduardo Bonilla-Silva, I noticed that some people were using racism somewhat synonymously with “structural racism”, i.e. “the outcome of systems that, intentionally or not, benefit one racial group over another/treat one racial group as more worthy”. Racist, then, can mean something more like “a person who, intentionally or not, supports systems that benefit one racial group over another/treat one racial group as more worthy”. It’s possible that there were folks who had always used these words these ways and I was only noticing it then because of what I was reading, but my impression is that in the late 00’s/early 10’s this usage became much more prevalent in certain groups.
And, it kind of makes sense: If you’re talking a lot about a particular topic you’ll notice details, minor differences that you want to be able to succinctly describe. You want your words to capture what you’re seeing, and if you’re not seeing many people openly expressing bigoted beliefs but you are seeing these harmful structures it makes sense to adapt your language. This happens all the time: it’s called jargon. For an example from software engineering: we often distinguish between “text files” and “binary files”, even though text is also stored as binary on disk.
But there are problems when people from different groups use the same word to mean different things. For an extreme example, my middle-school French teacher told a story about the dirty looks she got when taking her daughter to the zoo, and pointing out the seals: “un phoque!” (pronounced a lot like ‘fuck’). That’s a different language and people were upset about it. When people who think racist means bigoted talk to people who think racist means something structural, there’s understandable confusion. You can even have someone saying “I’m not a racist” (I don’t think less of someone because of skin color) and someone else saying “yes you are!” (you’re supporting this system), and they’re both right (each from their own perspective).
So, next time you find yourself at odds with someone, it might be worth double-checking: are you even talking about the same thing?