Modern English and Modern German are closely related languages. Generally, when linguists say something like this, it mainly means something like “there once existed another language which was neither Modern English nor Modern German, yet which is common ancestor of both languages”. Of course something as complex as a language can hardly be described in great detail, but this way of speaking about language / languages is common practice (and is also perhaps not very widely, but at least somewhat generally known).
One distinction between Modern English and Modern German is very much a development of the influence of written language norms. Back in the Middle Ages, Latin was usually written without much attention to the separation of individual words. This may have gradually changed over time, but both Modern English and Modern German are very distinct from the Latin predecessor(s) in this respect. Of course Gutenberg’s printing press (and of course also later printing presses) were very influential in this development in written language.
And yet there is also a significant distinction between Modern German and Modern English regarding the spacing between words, which seems to have little to do with “information and communication technology” (such as the printing press) and much more to do with things like regulations which are usually not interpreted as technological matters but rather as matters of language, nationality, … and generally social norms. [1]
Modern German is a very strongly regulated language. I wish to completely sidestep addressing which regulatory bodies are involved in “organizing” the regulations, but in contrast Modern English seems rather unregulated and chaotic. One such difference in regulation has to do with word boundaries (predominantly in written text). Since Modern German is regulated by rules (i.e. algorithms), it is possible to create words algorithmically — quasi “on the fly”. So (for example) while in English language countries the concept “Main Street” is quite widespread, in German language countries the algorithmic approach is so widespread that the single word “Hauptstrasse” is completely regular and accepted as the norm.
Personally, I feel as though when two words are “mashed up” as one word, the meanings of the two-word phrase and single mashed-up word must be distinct [2].
This is also a concept widely applied in linguistics — usually referred to as a “minimal pair”. [3]
My hunch is that if there is indeed a distinction between strings like “main street” and “mainstreet”, then it vaguely seems to have to do with something like the distinction between “a” and “the” (i.e. “indefinite article” vs. “definite article; yesterday, I attempted to explicate this some more — see also “ONE WAY + Many Views” [ https://indigenous.news.blog/2023/11/24/one-way-many-views ] … haha, I’ve been thinking about this crap for quite some time already 😉 ).

Now I can finally get to (or “make“) my main point: when we say “mainstream”, do we mean “a main stream” or “the main stream”? I actually predominantly think of “mainstream” as an adjective — but that still doesn’t actually resolve the issue for me.
I guess that I still don’t know. [4]
