Secondary Migration: Secondary migration as it pertains to refugees refers to any voluntary relocation of individuals after their initial placement.

Learn more at: http://www.unhcr.org/4e5f9a079.pdf

Principal City: “The largest city in each metropolitan or micropolitan statistical area is designated a ‘principal city.’ Additional cities qualify if specified requirements are met concerning population size and employment.”

Learn more at: https://www.census.gov/programs-surveys/metro-micro/about.html

Micropolitan Statistical Area: Micropolitan statistical areas consist of at least one urbanized cluster of at least 10,000 or no more than 50,000, and are defined on “county-based functional regions associated with the urban center”.

Learn more at: https://www.gpo.gov/fdsys/pkg/FR-2010-06-28/pdf/2010-15605.pdf

Metropolitan Statistical Area (MSA): MSAs consist of at least one urbanized area of 50,000 or more, and are defined on “county-based functional regions associated with the urban center”.

Learn more at: https://www.gpo.gov/fdsys/pkg/FR-2010-06-28/pdf/2010-15605.pdf

Urban Fringe: the densely settled surrounding area of a city.

Learn more at: https://www2.census.gov/geo/pdfs/reference/GARM/Ch12GARM.pdf

Urbanized cluster: An urban cluster consists of densely settled territory that contains at least 2,500 people, but fewer than 50,000 people.

Learn more at: https://www2.census.gov/geo/pdfs/reference/ua/Defining_Rural.pdf