The definition of the homeless can vary from country to country because homelessness is essentially a cultural definition based on concepts, which can be perceived in different ways by different communities. The following two categories or degrees of homelessness are recommended: (a) Primary homelessness (or rooflessness). This category includes persons living in streets or without a shelter that would fall within the scope of living quarters; (b) Secondary homelessness. This category may include the following groups: (i) Persons with no place of usual residence who move frequently between various types of accommodation (including dwellings, shelters or other living quarters) and (ii) Persons usually resident in long-term (also called “transitional”) shelters or similar arrangements for the homeless.