t is the time period between jobs when a worker is searching for or transitioning from one job to another.
Source: Boundless. “Types of Unemployment: Frictional, Structural, Cyclical.” Boundless Economics. Boundless, 21 Jul. 2015. Retrieved 06 Sep. 2015 from https://www.boundless.com/economics/textbooks/boundless-economics-textbook/unemployment-22/introduction-to-unemployment-102/types-of-unemployment-frictional-structural-cyclical-390-12487/