Disentangling the Polysemous Character of Sustainability in English Specialised Discourse

Sustainability is a pervasive yet conceptually unstable keyword in contemporary discourse. While often described as a ‘boundary term’ capable of aggregating heterogeneous epistemic communities around a shared commitment, it also functions as a floating signifier whose meaning shifts across domains and communicative contexts. Despite its widespread association with climate change discourse, since the late Twentieth century, sustainability has often been used without clarification, leading to ambiguity and facilitating semantic dilution and greenwashing. Integrating the theoretical tenets of critical discourse analysis with the methodological techniques of corpus linguistics, this study presents a corpus-based investigation of the noun sustainability and the adjective sustainable in four specialised English corpora available on Sketch Engine, focusing on collocational and co-occurrence patterns. The four corpora represent environmental discourse (EcoLexicon English Corpus and Environment Corpus), scientific/social science communication (Elsevier Open Access CC-BY Corpus), and economic/institutional language (United Nations Parallel Corpus). The results reveal both convergence and divergence in usage across domains. Economic and environmental sustainability show strong, recurrent semantic connections, whereas instances of general, domain-neutral sustainability remain vague and poorly specified. Notably, such uses do not clearly distinguish between weak and strong sustainability, nor do they consistently foreground a specific sustainability pillar. This indeterminacy highlights sustainability as a case of complex lexeme, whose meanings emerge dynamically through ‘figure and ground’ mechanisms within discourse.