pääjaksoihin

Pääjaksoihin is a Finnish plural illative form of the noun pääjakso. A pääjakso, literally meaning "main period" or "major phase," refers to a primary division within a larger sequence, such as a project, program, curriculum, or historical timeline. The term emphasizes that the whole is subdivided into significant segments rather than a random set of tasks.

Grammatically, pääjakso is formed from pää- (main) and jakso (period, phase, episode). The ending -iin marks the illative plural: pääjaksoihin means "into main periods" or "into main phases." It is used with verbs that express division or organization, for example: "Hanke jaetaan pääjaksoihin" (The project is divided into main phases), or "Opinto-ohjelma jaetaan pääjaksoihin" (The study program is divided into main periods).

Usage and scope: The expression is common in administrative, educational, business, and historiographical contexts when outlining structure, planning, or scheduling. It implies a deliberate segmentation into larger, meaningful parts rather than smaller, incidental units. In everyday speech, speakers may use more general terms such as vaiheet (phases) or jakso (period), but pääjaksoiin specifically signals primary, overarching divisions.

See also: jakso, vaihe, aikakausi, pää (main).