Clinicians are often asked to document a patient’s ethnicity when requesting certain types of medical investigations. For example, the genomic medicine service in England wants this information to help guide the interpretation of certain genetic findings. In the US, a patient’s race might be similarly documented. However, the terms ethnicity, or race, or indeed ancestry, do not correlate well with genetic code differences and are instead interwoven with complex socio-cultural elements.  In this article, we explore why this information can be important in genetic medicine and discuss the problems around the words we use. We suggest that clinicians are mindful of the complexities and ambivalence around the use of different terminologies and be sensitive to patient understandings of these terms. (By Dr Melody Redman, https://jmg.bmj.com/content/early/2023/11/28/jmg-2023-109370 )