The software and the system which imitate the intellectual job which the brain of the human does with the computer. It means the thing of the computer program and the like where you understand the natural language which concretely, the human uses, does logical inference, studies from experience. As the applied example of AI, there is an expert system and which imitatesthe problem solving technique of the specialist machine translation system,a picture andunderstand the meaning of sound picture understanding system and a speech understanding system etc. which do translation automatically. Lisp and Prolog etc. are knownas the programming language which is suited fordescribingAI.