Homelessness describes the condition of people without a regular dwelling. People who are homeless are most often unable to acquire and maintain regular, safe, and adequate housing, or lack "fixed, regular, and adequate night-time residence." The legal definition of "homeless" varies from country to country, or among different entities or institutions in the same country or region.^{[dubious – discuss]}

The term homeless may also include people whose primary night-time residence is in a homeless shelter, a warming center, a domestic violence shelter, cardboard boxes or other ad hoc housing situation. American Government homeless enumeration studies also include persons who sleep in a public or private place not designed for use as a regular sleeping accommodation for human beings.

In western countries the large majority of homeless are men (75-80%), with single males particularly overrepresented.

The "unsheltered" are that segment of a homeless community who do not have ordinary lawful access to buildings in which to sleep. Such persons frequently prefer the term "houseless" to the term "homeless". Others may use the term street people which does not fully encompass all unsheltered in that many such persons do not spend their time on urban "street" environments, and to the contrary shun such locales and prefer to convert unoccupied buildings, or to inhabit mountains or, more often, lowland meadows, creeks and beaches