That is among the plausible definitions of "half-sized paper". LOL. But the A-series innovation makes it easier to imagine scaling content/resources because you

That is among the plausible definitions of "half-sized paper". LOL. But the A-series innovation makes it easier to imagine scaling content/resources because you don't have to "retypeset" in your brain. But, mostly, my fascination with A-series paper as an American is rooted in my utter disappointment that we refuse to use the metric system (even though every single American does without knowing it).