The general aim of this research is to illustrate how scientific terminology was stabilising in eighteenth-century British specialised dictionaries and in universal dictionaries of arts and sciences. These were encyclopaedic works in alphabetical order, which “sought to combine alphabetical entries with deference to the classification of knowledge” (Yeo 2001: 27). Recurrent lexical items, frequent patterns of disciplinary thinking, and emerging communicative conventions highlight the complexity of the scientific process through time (Taavitsainen et al. 2014: 148). They also reveal the underlying mechanisms which define the medical lexicon, and medical writing in general, as specialised language use, as “medical group language” (Gunnarsson 2011: 305). The approach is mainly qualitative: the analysis is carried out on a selection of medical terms representing macro-areas of interest in medical research and practice for the period considered (e.g. inflammatory diseases, anatomical description, surgical operations, etc.). Selection, reduction, recurrence, adoption, and adaptation make form (spelling and lexical variants), structure (entry components), and content (semantic and pragmatic, lexical and encyclopaedic load) converge, and stabilise their relationship disciplinarily as well as lexicographically and/or lexicologically.