The Element Encyclopedia of Witchcraft: The Complete A-Z for the Entire Magical World - Judika Illes 2005
There are various forms of transformation:
Witches and sorcerers willingly transform into animals and back to their original form.
Animals willingly transform into people and back to their original form.
People are victimized, most frequently by witches, and forcibly transformed into animals. Under a spell, they lack the power to transform back at will but need magical assistance.
Werewolf literally means “man-wolf,” however there is some evidence that the word was originally used to indicate “one who knows how to change form.” That said, that word’s historical nuances and implication have cause werewolves to be unique phenomena, somewhat different from standard shape-shifting. Werewolves are discussed in depth together with wolves. See Wolves and Werewolves.