Writers: grammar is just rules for words. When rules don't fit, we must not quit. Let us pledge to bend or break any rules obstructing the storied paths of justice. Great writers tell their inner grammar ("and usage!") police when to freeze and look away.
Veronica Roth, for example, consciously eschewed convention when naming the five factions of her Divergent series.
According to this post on Roth's blog:
“People have... asked me why the faction names are different parts of speech-- three nouns (Candor, Amity, Abnegation) and two adjectives (Dauntless, Erudite). (For the record, I love this kind of grammar consciousness.) I am aware of that, and it was something I thought about in revisions. The reason for the discrepancy is that each faction chose their own names independently, just as they wrote their own manifestos independently, and formed their own customs and rules independently (to a certain extent, anyway). Keeping that in mind, I tried to pick the words that made the most sense for each faction without considering the other factions too much... And... (since I'm being honest, here)... they sound cooler."
She's right, of course. (Millions of fans can't be wrong.) We all benefit from Roth's calculated grammatical rebellion.
Here's a second example, from my YA science fiction novel Blaze – in which 16-year-old protagonist Blaise Davis struggles with adoption-related anger issues:
Stupid adopted dad. (Adoptive, actually, Blaise knew, but who said that? "This is my stupid adoptive dad." No one. No one ever said that.)
Okay, so I hedge my bets here. Blaise uses the wrong word ("adopted") because the wrong word just sounds right. Then he corrects himself ("adoptive") and explains why. The reason for this is:
Please join me. Don't be the bad cop.
Writer, reader, runner, teacher, father, infp, huffleclaw.