Why aren't British and American English considered separate languages?

True enough. However, the varieties we think of as traditional dialects of German are in many places disappearing. They are being ousted by regional spoken varieties of standard German. For instance, the Berlin dialect is very distinct but it is basically a mixture of dialect and standard German.

Chinese is of course an interesting question in itself. Southeast China has all those Chinese languages - Cantonese, Hakka and the rest - and many Chinese communities outside mainland China actually use non-Mandarin dialects, because much of coastal China is traditionally non-Mandarin-speaking. However, I have been reliably informed that ethnic Chinese communities outside China are in varying degrees turning to Standard Mandarin Chinese even where the traditional language of the community has been non-Mandarin (Min Nan Chinese, for instance, is widespread in such communities eastern Asia). Young ethnic Chinese in those parts do not speak their ancestral variety anymore, but study Standard Mandarin as a heritage language.

You’re talking about Chinese outside of China. That’s interesting in itself, but surely talking about Chinese within China is more useful. Ethnologue says that there are fourteen different Chinese languages. Glottolog says that there are twenty-two different Chinese languages:

http://www.ethnologue.com/subgroups/chinese

http://glottolog.org/resource/languoid/id/sini1245

I’ve read news stories that say that even these two counts are an underestimate of the number of different Chinese languages if you count every mutually unintelligible variety. These stories say that the Chinese government discourages foreigners from visiting rural villages because they don’t want to let them know how different the variety of Chinese spoken there is from the Chinese language they supposedly speak. These stories say that really there are more like forty different Chinese languages.

If you count every mutually unintelligible variety, of course there will be lots of “languages”, but those varieties can usually be classified into higher order groups of related dialects. We actually know a lot about Chinese languages and their mutual relationships - many Chinese emigrants actually have organized to promote their respective languages. I remember having found Hakka Chinese nationalist sites online, for instance.

The problem, supposedly, is that the fourteen Chinese languages are not really groups of dialects where all the dialects in each group is mutually intelligible with all the others. The problem, supposedly, is that you would have to put together the hundreds of Chinese dialects into maybe forty groups to get to the point that the dialects within each group are all mutually intelligible with each other. That makes each of those forty or so groups a language with half a dozen to a dozen dialects each, supposedly. Supposedly, the Chinese government knows this and is trying to keep other people from realizing it.

My college German-language professor earned his doctorate through a study of medieval Low German. He told my class an anecdote of a later personal experience: he had traveled to the German-speaking area of Switzerland to learn Alpine skiing. The first thing the Swiss instructor said to his class, in standard German, “Wer spricht Schwytscherdeutsch?” (Who speaks Swiss German?) It turned out that every ski student, except my professor, was a Swiss German, and he thought, “Uh-oh…Swiss German?” Since he was the sole non-Swiss German, instruction proceeded solely in Swiss German. After a few minutes of listening, though, he realized that Swiss German was actually nearly the same as medieval Low German! A day or two later, he was chattering away so easily in Schwytscherdeutsch that the other students, surprised, asked him where he was from–and were astounded to get “Ohio” as a response.

American Sign Language is descended primarily from what sign language linguists call the Old French Sign Language, blended with heavy influence from the now-defunct deaf sign language of Martha’s Vineyard, Massachusetts. OFSL was brought to America in 1817 by the deaf French teacher of the deaf, Laurent Clerc, who was co-founder of the U.S.'s first permanent school for the deaf (now the American School for the Deaf in Hartford, Connecticut). A number of the school’s early students came from the Martha’s Vineyard deaf community, hence the source of that “DNA”. Today’s French Sign Language has evolved enough from OFSL that linguists now distinguish between the two, but they still retain much intelligibility with each other–and with their American Sign Language descendant/cousin.

To illustrate this, right around 1980, I was manning a service desk in the Gallaudet University Library when a group of deaf French visitors came through and stopped near my desk for an explanation of the library. I didn’t know French Sign Language, so I watched what was going on. The deaf Gallaudet tour guide would say something in ASL, a hearing American interpreter would render it into spoken English, a hearing member of the French group who also knew English would translate it into spoken French, and finally a French Sign Language interpreter would put the spoken French into FSL. Whenever a deaf member of the group asked a question, it moved up the chain in the opposite direction. That was fascinating enough, but what was even more interesting to me was that I soon realized I could cut out all the “middlemen” and just watch the ASL on one end and the FSL on the other end, with something like 95% of full understanding. Yet, applying common linguistic tests of languages vs. dialects, ASL and FSL are usually considered separate languages.

Most estimates say that the number of common signs between American Sign Language and Old French Sign Language is considerably less than 95%. One account says it’s 58%, and the percentage in common between American Sign Language and modern French Sign Language is less than that. The relationships between the various sign languages is a mess that no one has done a good study of. Not only is there the relationship between the American and the French varieties, but there are various other sign languages in the world that have been influenced by the American variety. There are also influences from the various spoken languages. There really ought to be some serious academic studies of relationships between the many varieties of sign language.

Québec dialects developed when recent migrants to New France had to find a common tongue to talk to each other. The bulk of the early settlers came from Normandie, the greater Parisian region and the south west of France. The Parisian dialect, which had by that time became the standard in France was chosen, but it was greatly influenced by the various patois spoken by the settlers.

Nevertheless, 17th and 18th writers describe the language spoken in New France as “lacking an accent” and being generally very close to ideal, despite a few regionalisms. However, perhaps owing to the relative isolation after the British took control of Canada, Québec French evolved somewhat differently from continental French, and in the process retained certain characteristics that were lost in standard French French.

One of the more notable of these is the pronunciation of certain diphthongs, where the older form was retained. For instance, oi is pronounced /we/ instead of /wa/. Toi et moi becomes thus, toé pi moé, where pi likely comes from the Picard language. Furthermore, a few archaic words are still in common use, such as boucane (smoke).

Note that this is true only for the spoken vernacular. Formal language in Québec is, in theory, identical to that in France. In practise, there are certain differences as far as vocabulary is concerned and of course the accents are very different. Nevertheless, if you were given a random excerpt from a novel, it would be very difficult, if not impossible to tell if the author was French or Canadian.

I don’t know where you’re getting the idea that the Chinese government is trying to keep that particular linguistic issue a secret from, well, anyone. I live in Beijing and from all indicators I see and hear here, the government is aware that Chinese is a group of languages with a (mostly) uniform writing system, and that each of those languages has a number of dialects. Although the government has designated that one particular dialect of one particular Chinese language is the national language, that does not mean that educated people are unaware that dialects for their local language is mutually–or even at all–intelligible with another dialect of that same language, let alone with a different language in the Chinese group.

Here’s what I’ve read. Everyone with any linguistic training knows that Chinese isn’t a single language. The standard line among linguists is that there are perhaps about fourteen different languages among those that are usually referred to as Chinese (i.e., you could break up the speakers of Chinese into perhaps fourteen groups so that everyone within each group could understand everyone else within that group). The Chinese government acknowledges the differences among these various varieties, but they also insist on referring to each of these as “dialects,” as if they were mutually intelligible. They want to pretend that they are closer than they actually are.

However, some linguists outside of China who’ve actually managed to listen to speakers in rural villages say that even fourteen different languages is an underestimate. One thing I read said that it would be more accurate to describe Chinese as a group of forty to fifty languages. The only reference I’ve found online (given below) says that it may actually be hundreds of languages. The things that I’ve read claim that the Chinese government discourages foreigners from visiting rural villages so that foreign linguists won’t realize how many different Chinese languages there are. Note that I’m only talking about the Han peoples. There are, of course, also the various unrelated languages spoken in China which everyone, including the government, acknowledges are different languages:

A bit of a nitpick, Scots is a language that is (or was) spoken in the Lowlands, and also Ulster - hence the alternate name “Lallands”. The native language in the Highlands was Gaelic, a language no more related to Scots than it is to English.

I’m not seeing discouragement of rural visits by foreigners in that link. I’m certainly not seeing such discouragement today by the Chinese government.

And studying multiple languages that are related helps you fill in the likely gaps in your knowledge of others. For example, an English speaker who also knows German stands a better chance of understanding Old English or Middle English than someone who knows just Modern English. E.g. Chaucer used several now-obsolete or archaic English terms that have modern-day cognates in German. E.g. “wend” as a verb, and the noun “holt” to mean forest. Add two semesters of Swedish and he gets even better, more able to recognize Norseisms that are no longer favored in modern English.

I would totally not be surprised if someone who knows modern French and has studied some classical Latin, modern Spanish, and also has a good command of English would be able to read medieval French documents.