RANKL is a protein that plays a significant role in the regulation of bone metabolism, lymphoid organ development, and the immune response. The term RANKL is shorthand for "receptor activator of nuclear factor kappa-Β ligand," which is its primary function. However, there are several other names and synonyms for this protein, including TRANCE (tumor necrosis factor-related activation-induced cytokine), OPGL (osteoprotegerin ligand), TNFSF11, ODF (osteoclast differentiation factor), and many others. These synonyms are useful for better understanding the many roles that RANKL plays in human physiology, as well as for researchers studying this protein and its related pathways. By using a variety of different terms, scientists can gain new insights into the complex mechanisms of bone metabolism and immune system regulation.