(i) A personality purporting to be that of some deceased individual, believed to take control of the medium’s actions and speech during trance, and/or who habitually relays messages from the communicator to the sitter. (ii) In the context of scientific investigation, a control is something (a procedure, condition, object, set of subjects, and so on) which is introduced with the purpose of providing a check on (that is, of “controlling for”) the influence of unwanted factors.