underclass a small group of people for whom poverty persists year after year and across generations

underemployment the condition of having to work at a job beneath one’s level of training and abilities, or of being able to find only part-time work

underground economy exchanges of goods and services that are not reported to the government and thereby escape taxation

unitary state form of government in which all power resides with the central government

universal citizenship the idea that everyone has the same basic rights by virtue of being born in a country (or by immigrating and becoming a naturalized citizen)

unobtrusive measures various ways of observing people who do not know they are being studied

unstructured interviews interviews that use open-ended questions

upward social mobility movement up the social-class ladder

urban ecology the study of the link between the physical and social dimensions of cities

urban legend a story with an ironic twist that sounds realistic but is false

urbanization the process by which an increasing proportion of a population lives in cities