halcyonhours asked: Aspiring linguist here: A word becomes a word when someone actually uses it. Sonder became a word since the moment someone gave it meaning, so, I don't know if it'd be academically accepted by teachers, but it is a word indeed and completely valid to use. Just check the works of David Foster Wallace and count the number of "made-up" words :) It's completely valid.

Answer moved here, and here’s why.