Homelessness is the conition and societal category of people who lack housing and food, usually because they cannot afford a regular, safe, and adequate shelter. The term "homelessness" may also include people whose primary nighttime residence is in a homeless shelter, in an institution that provides a temporary residence for individuals intended to be institutionalized, or in a public or private place not designed for use as a regular sleeping accommodation for human beings. A small number of people choose to be homeless nomads, such as some Romani people (Gypsies) and members of some subcultures. An estimated 100 million people worldwide are homeless.