Bioethical decisions are present in every clinical decision. Nutrition support participates the same situation. Feeding critically ill patients, etriminal patients or in permanent vegetative status is almost always involved in bioethical dilemmas. A common problem is the confusion in concepts regarding bioethics. This lack of uniformity does not help in the deliberation process. From the Working Group in Bioethics of the Spanish Society for Parenteral and Enteral Nutrition Support (SENPE) it has been considered to gather the commonest terms used in our academic area. Each term is accompanied by a definition, a description or a commentary related to its main application.