Short-term labour and precarious work formed an important and organic part of pre-industrial society. The introduction highlights various social and occupational groups who, instead of owning land or holding fixed-term employment, lived on short-term, parallel, and/or seasonal work in the Nordic context, particularly in Finland, in both the urban and rural context in 1620–1870. The introduction also explores the factors behind the extent and prevalence of short-term labour and precarious work in pre-industrial society. The primary causes—often intertwined and overlapping—were (1) seasonal variation, which inevitably resulted in periodic employment due to the Nordic climate; (2) significant fluctuations in population and the labour force (population disasters/growth); (3) institutions that fostered short-term employment (such as obligatory service, legal protections, and restrictions on self-employment and land ownership); and (4) the state formation process, especially as it influenced employment in the army, county administration, and church. Additionally, a person's health or (dis)ability could influence his or her ability to engage in work. Simultaneously, the definitions and meanings of short-term work and precarious labour in early modern society are examined.