The U.S. Department of Housing and Urban Development (HUD) defines the term homeless or “homeless individual or homeless person” as (1) an individual who lacks a fixed, regular, and adequate nighttime residence; and (2) an individual who has a primary nighttime residence that is (a) a supervised publicly or privately operated shelter designed to provide temporary living accommodations (including welfare hotels, congregate shelters, and transitional housing for the mentally ill); (b) an institution that provides a temporary residence for individuals intended to be institutionalized; or (c) a public or private place not designed for, or ordinarily used as, a regular sleeping accommodation for human beings.

In recent years, the homeless population in the United States has changed in important ways (Table 37-1). The “new” homeless population is younger and much more mixed: more single women, more families, and more minorities. Lower economic levels affect parents because of the effect on their psychological well-being. Distressed parents state they feel less effective and capable and are less affectionate in their interactions with their children.

It is difficult to estimate the number of homeless in the United States, but reports have ranged from 300,000 to 800,000. In 2006, the Associated Press reported that there were more than 700,00 homeless in the United States.