Aggression
Behaviour intended to create distance or hold onto something — growling, snapping, biting — and almost always rooted in fear rather than dominance.
Also called: aggressive dog · dog aggression · bite history
Aggression is communication with the volume turned up. A dog that growls is telling you it wants something to stop, and it has usually already tried three quieter ways of saying so — turning its head, freezing, showing the whites of its eyes — that nobody noticed.
This is why punishing a growl is the most expensive mistake an owner can make: it removes the warning without touching the feeling underneath, and the next dog you meet is one that bites without growling first.
Cases with a bite history are not a harder version of ordinary training; they are a different job, with management, safety and often a vet involved from the start.