The prescriptive school of thought in terminology holds that terms should be fixed items and should not be prone to variation. More recently, however, descriptive studies have begun to reveal that many terms do in fact have variants. This poses a challenge for language professionals such as translators and terminologists, who need to decide which form of a term to use in a given context. This article explores one specific type of variant that occurs frequently in medical language — variants that can be formed by combining elements of a term in a different order (e.g. cardiovascular vs. vasculo­cardiac). By studying such variants in corpora, we have identified some regular patterns that appear to reveal conceptual, linguistic and social motivations behind term choice. An understanding of these factors may help translators and terminologists to choose the most appropriate term.