This article examines some aspects of the conceptual, lexical and terminological levels of the process of encoding and decoding. The study of the structures and the functions of standard units on the cognitive and semiotic level is very important in the light of lexicological, semantic and terminological research. On the one hand, the structural and functional complexity of formations on the highest level (concept, metaconcept, meta-metaconcept) is highlighted. On the other hand, conceptual and methodological differences are examined which characterize the concept and the definition. That way a methodology is proposed to formalize the semantic-conceptual features of a given concept.