Language shapes beliefs and may influence behaviours. Considered use of appropriate language has the power to strengthen the global response to the AIDS epidemic. That is why the Joint United Nations Programme on HIV/AIDS (UNAIDS) is pleased to make these guidelines to Preferred terminology freely available for use by staff members, colleagues in the Programme’s 11 Cosponsoring organizations and other partners working in the global response to HIV. These guidelines are a living, evolving document that is reviewed on a regular basis. This revision of the 2011 edition has discarded a few terms and added new ones that are relevant to the global response to HIV and commonly used by UNAIDS.