The term "Rh antigen" is commonly used to refer to the protein molecules found on the surface of red blood cells. These proteins play a crucial role in determining an individual's blood type and can potentially trigger an immune response if introduced to a person with a different Rh status. There are several synonyms for Rh antigen, including the Rh factor, the Rhesus factor, D antigen, and D factor. These terms are often used interchangeably in medical settings and are important for understanding blood transfusions and pregnancy complications related to Rh incompatibility. It's essential to know these synonyms and their definitions to communicate effectively with healthcare professionals and ensure patient safety.