Knowledge is a model that enables premeditated change. Knowledge can be subdivided: the simplest element is information. Information aggregates/relations constitute a concept. Clusters of concepts make theories. Concepts and theories can be further branched into: conclusions, explanations, cognitions, etc, which together belong to a general class of Definition. Definitions are key elements of knowledge. Yet it appears that we do not sufficiently explain the nature of this concept of definition itself. There is little doubt about the importance of words and languages, however these semantic structures contain some intrinsic ambiguities. Knowledge records grow faster than its substance, and it is increasingly difficult to manipulate and communicate this voluminous structure. The interpretations of terms and knowledge can vary significantly, especially in the multidisciplinary context. Misiformation is exacerbated by vague definitions including synonyms, homonyms and acronyms. This paper attempts to contribute to defining the term ‘definition’ to alleviate the mentioned problems.