The term AUTOMATON (PREF.) can be solved by the four-letter word ROBO. AUTOMATON is a term used to describe a self-operating machine or robot, which is able to carry out a complex series of actions automatically. The prefix 'AUTO' means self, and the suffix 'maton' comes from the Greek word for 'one who imitates'. Therefore, the term 'AUTOMATON' literally means 'self-imitating one'. The word 'robo' is derived from the Latin word 'robotem', which means 'forced labor'. Thus, the term 'robo' is used to refer to a machine or robot that performs tasks without the need for human intervention.