Is it a real word?...I guess it just depends on how you come to define words..as someone said...every word is made up at some point. Until it become real due to usage.
I like the idea of "sonder"...a word my computer's internal dictionary certainly does NOT recognize. It is a small word for a very thoughtful and complex meaning.
And I like that it causes you to reflect. As I am in the midst of traveling now heading from WI to FL and amidst so many new people...it is a great travel word.
n. the realization that each random passerby is living a life as vivid and complex as your own—populated with their own ambitions, friends, routines, worries and inherited craziness—an epic story that continues invisibly around you like an anthill sprawling deep underground, with elaborate passageways to thousands of other lives that you’ll never know existed, in which you might appear only once, as an extra sipping coffee in the background, as a blur of traffic passing on the highway, as a lighted window at dusk.
I found a tiny video that I think really is THE best definition for this word. Take a look here. See what you think.