The definitions in this glossary are adapted from the following publications by the Interagency Working Group on Key Populations (all published by WHO, 2015).

as well as the Discussion paper: Transgender health and human rights (UNDP, 2013)

Adolescents are those aged 10–19 years.

Young people are those aged 10–24 years. 

Young sex workers include female, male and transgender adults (18 years of age and above) who receive money or goods in exchange for sexual services, either regularly or occasionally. Sex work is consensual sex between adults, can take many forms, and varies between and within countries and communities. Sex work may vary in the degree to which it is “formal”, or organized. 

Sexually exploited children refers to the exploitative use of children (under 18 years of age) in prostitution, defined under Article 2 of the Optional Protocol to the CRC on the sale of children, child prostitution and child pornography (2000) as “the use of a child in sexual activities for remuneration or any other form of consideration”.

Adolescent boys and young men who have sex with men refers to males aged 10–24 who engage in sexual and/or romantic relations with other males. The words “men” and “sex” are interpreted differently in diverse cultures and societies, as well as by the individuals involved. Therefore, the term “men who have sex with men” encompasses the large variety of settings and contexts in which male-to-male sex takes place, across multiple motivations for engaging in sex, self-determined sexual and gender identities, and various identifications with particular community or social groups. 

Transgender is an umbrella term for all people whose internal sense of their gender (their gender identity) is different from the sex they were assigned at birth. Transgender people choose different terms to describe themselves. Someone born female who identifies as male is a transgender man/boy. He might use the term “transman”, “FtM” or “F2M”, or simply “male” to describe his identity. A transgender woman/girl is someone born male who identifies as female. She might describe herself as a “transwoman” “MtF, “M2F” or “female”. In some cultures, specific terms such as hijra (India), kathoey (Thailand) or waria (Indonesia) may be used.

Gender non-conforming (or gender variant) refers to people whose gender expression is different from societal expectations and/or stereotypes related to gender.

People who inject drugs refers to people who inject non-medically sanctioned psychotropic (or psychoactive) substances. These drugs include, but are not limited to, opioids, amphetamine-type stimulants, cocaine, hypno-sedatives and hallucinogens. Injection may be through intravenous, intramuscular, subcutaneous or other injectable routes. This definition of injecting drug use does not include people who self-inject medicines for medical purposes, referred to as “therapeutic injection”, nor individuals who self-inject non-psychotropic substances, such as steroids or other hormones, for body shaping or for improving athletic performance.