We focus on the dynamics of colexification, a process whereby different meanings are expressed by the same word, and its opposite, de-colexification, in language and culture contact. In multilingual environments, colexification of reference to two celestial entities – ‘sun’ and ‘moon’ – enhances intertranslatability and ease of communication between coexisting languages. The terms for ‘sun’ and ‘moon’ in two extant dialects of Tariana, the only North Arawak language in the multilingual Vaupés River Basin Linguistic Area, are a case in point. Under the influence of neighbouring majority East Tukanoan languages, the terms for ‘sun’ and ‘moon’ underwent colexification in one Tariana dialect. The recent nature of contact-induced colexification is evidenced in the ways the colexified term – which goes back to the Proto-Arawak ‘moon’ – preserves the original meaning ‘moon’ in various expressions. ‘Moon’ and not ‘sun’ is the target of colexification due to its magic powers and the frequency of its mentions, as a driving force in language change. Speakers of the other extant dialect of Tariana demonstrate the opposite process of de-colexification of ‘sun’ and ‘moon’, resulting from intensive contact with the closely related Baniwa of Içana. Communicative necessity to express matching concepts drives colexification and its demise.

Previous studies have proposed that the lexicalization of perception verbs is constrained by a biologically grounded hierarchy of the senses. Other research traditions emphasize conceptual and communicative factors instead. Drawing on a balanced sample of perception verb lexicons in 100 languages, we found that vision tends to be lexicalized with a dedicated verb, but that nonvisual modalities do not conform to the predictions of the sense-modality hierarchy. We also found strong asymmetries in which sensory meanings colexify. Rather than a universal hierarchy of the senses, we suggest that two domain-general constraints—conceptual similarity and communicative need—interact to shape lexicalization patterns.