Homelessness or houselessness – also known as a state of being unhoused or unsheltered – is the condition of lacking stable, safe, and functional housing. The general category includes many disparate situations, including:
living on the streets, also known as sleeping rough (primary homelessness)
moving between temporary shelters, including houses of friends, family, and emergency accommodation (secondary homelessness)
living in private boarding houses without a private bathroom or security of tenure (tertiary homelessness)
having no permanent house or place to live safely
Internally Displaced Persons, persons compelled to leave their places of domicile, who remain as refugees within their country's borders
The rights of people suffering from the devastating effects of homelessness also vary from country to country. United States government homeless enumeration studies also include people who sleep in a public or private place, which is not designed for use as a regular sleeping accommodation for human beings. Homelessness and poverty are interrelated. There is no methodological consensus on counting homeless people and identifying their needs; therefore, in most cities, only estimated homeless populations are known.
In 2005, an estimated 100 million people worldwide were homeless, and as many as one billion people (one in 6.5 at the time) live as squatters, refugees, or in temporary shelter, all lacking adequate housing.
Scarce and expensive housing is the main cause of rising homelessness in the United States.
In 2004, the United Nations sector of Economic and Social Affairs defined a homeless household as those households without a shelter that would fall within the scope of living quarters due to a lack of a steady income. The affected people carry their few possessions with them, sleeping in the streets, in doorways or on piers, or in another space, on a more or less random basis.