 We all know basically what language is. It's that thing you do when you know something and someone else doesn't know something so you flap your tongue around and suddenly they know the thing. Or in the case of sign language, you wave your arms around or, for written language, you draw lines on things and I guess there's also, like, Morse code and stuff and... Okay, back up. Let's try this again. A language is a system of communication. A set of norms for turning ideas and information into symbols and different languages are different such systems. Okay, but people in England call elevators lifts, so that means they have a different system for turning information into symbols. So do they speak a different language? Well, no, of course not. The Brits might have a few different words for a few different things, but for the most part they call stuff by the same words we do, and also for the most part have the same grammar we do. Okay, but it's not just those words. They pronounce basically all of their words differently than we do. Saying bet-uh instead of better, both instead of bath, the list goes on. Yeah, but that's just minor differences in pronunciation. You still know what British people mean when they say both instead of bath. That means we're not dealing with different languages, just different accents, right? And here, we get to the rule that linguists actually use to distinguish between languages, mutual intelligibility. If two people can't talk to each other and understand each other, then there is no mutual intelligibility and they're speaking different languages. If, on the other hand, they can communicate with each other, then there is mutual intelligibility and they're speaking the same language. It's worth noting though, linguists don't really like using the term accent in this context. If two people speak differently but can still understand each other, then they pretty much always say that they speak two different dialects. This is because the term accent carries this connotation of wrong or weird or, at the very least, non-standard, which is the sort of cultural value judgment we should probably be trying to avoid. So, that pretty much covers it. Languages are defined by mutual intelligibility. Come back for my next video. Okay, it's more complicated than that, for a lot of reasons. Let's start with one of the most notable cases of confusion, the Chinese languages, where you have a whole bunch of different dialects of Chinese that are so different that speakers usually can't understand each other. This should mean that they're different languages, and most of the time that's how we talk about them. These days, people tend to talk about Mandarin Chinese versus Cantonese versus Hakka versus Wu, etc., all as different languages. And yet, all of these people still use the same Chinese characters to write with, and can therefore communicate with writing just fine. So, we find ourselves in the awkward position of saying that they speak different languages, but write in the same language. Another good example of where all of this gets much more complicated is the phenomenon of dialect continuums. Say, person A and person B speak with mutual intelligibility. Their speech is a little different, just like between the US and Britain, but for the most part they can still understand each other. Likewise, person B can understand person C, and person C can understand person D. But try to get person A and person D to talk to each other, and they have no idea what the other one is saying. Each dialect these people speak is just a little bit different from the ones on either side, so that eventually you've completely lost mutual intelligibility. By our earlier rule, person A and B speak the same language, as do B and C and C and D. And yet, at the same time, person A and D speak different languages. Unfortunately for linguists, this kind of thing happens in real life all the time. And when it does, they usually just call the whole system a dialect continuum. It most famously happens a lot in Africa, where a lot of the time each town will be able to talk to the next town over with relative ease, but the further away from your home you go, the less you can understand people. But perhaps the biggest obstacle for the use of this rule is the fact that there is no solid line between mutually intelligible and not mutually intelligible. Even American English speakers and British English speakers will have a harder time understanding each other than they would someone from their own continent. And even people who speak languages completely unrelated to each other might still get a little bit of information out of each other if they can pick out a few loanwords. In between, there's a huge, infinitely divisible spectrum of levels of intelligibility, where you have the difference between some romance languages, where you can understand a lot, maybe even the majority, but never everything, or the difference between English and German, where you can't understand most of it, but every now and then you might hear something like, Die Ses Buch ist gut, and get the general idea. On top of this is the fact that intelligibility isn't always symmetrical. Like how people from Denmark can understand people from Sweden way better than the reverse. A lot of things can cause this, like one language might have some sounds merged while the other has them unmerged, or one language might have more words that the two have in common and fewer of its own words. But usually the most important factor is when, for some historical reason or another, one country gets exposed to media from the other country way more than the other way around. In the end, one of the huge things that winds up playing a decisive role in whether people call two things different languages, or just different dialects of the same language, is politics. People who want to create a sense of national unity among a group of diverse people often make the case that they all speak the same language. While if you think that part of this group should be its own independent country, then you're more likely to say that they speak different languages. Hence, people in India and Pakistan will often talk about how India uses Hindi while Pakistan uses Urdu, even though speakers of the two can easily understand each other. And official documents back from Czechoslovakia used to talk about a Czechoslovak language, while these days people usually talk about a Czech language and a Slovak language. I wish there were a way for me to demonstrate partial intelligibility better. All I've really got to work with for English speakers are the difference between American English and British English, which is barely anything at all, and the difference between, like, English and German, which is enormous. Too bad there's nothing in between. Oh yeah, Scots! Like modern English, Scots is descended from Old English, which was spoken about a thousand years ago in Britain. But while English slowly changed into modern British English and England, Old English diverged and evolved into Scots in Scotland. Keep in mind that Scots is a completely different thing from Scottish Gaelic, a Celtic language spoken in Scotland before the arrival of the Anglo-Saxons, and it's also different from the Scottish dialect of modern English, which is the dominant language in Scotland today, and, like American English and British English, is descended from early modern English, although it does have a fair amount of influence from Scots. Scots, I think, is an amazing example for English speakers to learn what partial intelligibility feels like. For example, this awesome video gives a short history of Scots in Scots, and sometimes you can understand them perfectly, while other times you have no idea what he's saying. Most of the time, though, you get enough of an idea of what he's talking about to figure out the meaning of the words you don't know from context. At the same time, you get a very strong sense for how asymmetrical intelligibility can form. All I had to do was watch through this 20-minute video, and I was already picking up a lot of Scots' words without even really trying to. Lead for language, bilead for dialect, echt for eight, and I think similar might be something like sucklight. It's a really cool experience that English speakers don't get to often, and I think it's the best way to get your head around the fact that what does and doesn't count as its own language is often way fuzzier than people usually assume.