Today, term variation is commonly accepted to be a widespread phenomenon in specialised communication. Although some degree of arbitrariness is inevitable, the expert's choice of a term variant is generally motivated to some extent. This article presents a methodology for describing the conceptually motivated patterns of term variation in a real corpus of special language. This method — which analyses the conceptual information displayed on the term's form — represents an attempt to provide a framework accounting for the flexibility of concepts and conceptual structures in a systematic way. Using data from a bilingual (French and Galician) corpus of texts related to coastal fishing and aquaculture, the applicability of proposed method for analysis is illustrated with a description of the variation patterns pertaining to terms designating human entity concepts within the corpus.