The Royal United Services Institute for Defence and Security Studies (RUSI) is a well-known British think tank that focuses on issues related to defence and security. Although it is commonly known by its full name, there are several other synonyms that are used to refer to the institution. These include RUSI, the Royal United Services Institute, the Institute for Defence and Security Studies, and the Defence and Security Think Tank. Regardless of the name used, the institution is known for its expert analysis and research on a broad range of defence and security issues. RUSI has a long history of producing valuable insights and recommendations, and continues to be a respected voice in the field of international security.