Notes

an animagusis a wizard who can transform into an animal. The magic required is quite complex, and it can go badly if the wizard is not experienced enough to handle the transformation. While in animal form, the animagus retains many human abilities, but also becomes more animal like.

The form which an animagus takes is not determined by the individual wizard. Rather, the animal form reflects part of the wizard's inner nature. Throughout his or her lifetime, an animagus can apparently only take one animal form, although it is possible that this may perhaps change under immense emotional stress, just as a Patronus charm does.

The extremely advanced magic does not require the use of a wand. In addition, the wizard's clothing appears to be retained somewhere while he or she is an animal, because wizards are garbed again when they return to human shape.

It appears that while an animagus is in animal form, he or she may be able to communicate with animals. The brain and cognition processes of the wizard also appear to be slightly slowed. This distinguishes an animagus from a wizard who has been transfigured into animal shape, as transfiguration appears to cause the wizard to have an animal brain.