The DSM IV uses the terms "identity", "personality states" and "alternate identities" when talking about DID and other people use the term "alters" to mean the same thing. These words can be confusing since not everyone uses the same definition. Professionals have not agreed on a specific definition for a personality; other terms, including dissociation and amnesia, may also be defined differently by different professionals. When talking about DID, saying someone changes personalities or alters means the person speaks and acts differently, and usually responds to a different name.