This paper analyzes the application of usage labels in three representative lexicographic works, namely the Portuguese, Spanish, and French Academy Dictionaries as a starting point for creating a consistent classification of usage labels and their encoding in accordance with TEI Lex-0. The use of labels is not always entirely consistent within individual dictionaries and even less so across different lexicographic projects. This makes the tasks of accurately classifying and encoding them quite difficult. This difficulty is compounded by the differences and partial incompatibilities found in the lexicographic literature on the treatment of diasystemic information. We address the existing literature and the initial classification of TEI Lex-0, and argue for the need to introduce some changes to TEI Lex-0, most notably in terms of diatextual labels. Finally, we argue that the existing classifications based on examples rather than on clear and explicit definitions of classification categories will always lack in precision and lead to mutually incompatible encodings of different dictionaries. We propose a set of definitions for usage label categories that can be adopted by TEI Lex-0 and used in other similar attempts to create interoperable lexical resources. An agreement on usage label categories is a first and necessary step before proceeding in the direction of harmonizing and standardizing the actual values of usage labels across various dictionaries and across different languages.