Words know borders. Air can carry words only so far, relying on bodies to extend the range. Pages and books extend the range even further, but the irony is that on the page, words have never been more cloistered, more isolated from each other.
In the West, Latin letters were originally written in continuous lines, without spaces in between words. On papyrus and parchment, words followed each other in strings.
If the Romans had used computer keyboards, they wouldn’t have had a spacebar.
Scholars refer to this writing convention as scriptio continua, which is a slightly pedantic, though fully recognisable Latin way to say ‘continuous script’ or writing.
It was a poor reading aid, but a great economical feature. The ancients figured it out pretty quickly, like any pragmatic culture, that slack is a liability, and sought ways, even in letters, to reconcile the things of the intellect with the stuff of finance. For word separation meant more space, and more space led to more financial constraints.
Reading words in scriptio continua takes a level of familiarity with written language which I fear is far superior to that of the average modern reader. And when the language is inflected (i.e. words change form depending on their role in the sentence), the lack of word separation makes reading a cognitive adventure.