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. These guidelines may be freely copied and reproduced, provided that it is not done for commercial gain and the source is mentioned. Comments and suggestions for additions, deletions or modifications should be sent to terminology@unaids.org.