Although a set definition of a beast has been founded by the Magical World, there has always been a large controversy about it. There are three cases that make this very complicated:
1) Werewolves: Are they really a beast? They spend most of their time as Muggles or Wizards, and only once a month as a savage, four-legged beast.
2) Centaurs: Part horse, part human, they posses a great amount of intelligence. Thus, they live in the wild and prefer not to wear any clothing over their skin.
3) Trolls: Possessing a human-like appearance, this giant being has very minimal intelligence and no magic besides it's vast strength.
As this problem arose, so did controversy over what was really a beast. Therefore, the magical community finally agreed upon two definitions to categorize the creatures (Although there are three categories, Being Division, Beast Division, and Spirit Division):
1) Being: Any creature that has sufficient intelligence to understand the laws of the magical community and to bear part of the responsibility in shaping those laws.
2) Beasts: Anything that is not a ghost and does not fall under the being classification.
Although both the Centaur and the Merpeople fall under the being category, they have rejected it and have decided to remain under the Beast category. Also, creatures that cannot overcome their dangerous nature are classified as beasts, such as acromantulas. Hags and vampires, though, are beings.
Beasts, Beings, and Spirits are given a classification in order to asses how dangerous they can be to both the Muggle and Wizarding community. These rules have been set by the Department for the Regulation and Control of Magical Creatures. The five classifications are as follows:
(Referred to as Ministry of Magic, or M.O.M., Classification)
1) XXXXX -> Known wizard killer/impossible to train or domesticate
2) XXXX -> Dangerous/Requires specialist knowledge/Skilled wizard may handle
3) XXX -> Competent wizard should cope
4) XX -> Harmless/May be domesticated
5) X -> Boring