pääreittillä

Pääreittillä is a Finnish term used to describe the location or progression along the main route in hiking, transport, or planning contexts. The word is formed from pääreitti "main route" with the locative suffix -llä, yielding "on the main route." It denotes that something lies on, or should be followed along, the central, most-used path rather than on side paths or detours.

In outdoor recreation, pääreittillä often appears in maps, signs and guides to indicate that hikers or travelers should stay on the principal trail to remain on the designated route and to minimize environmental impact. In transportation and event planning, the term can refer to the primary corridor that connects key locations and is prioritized for maintenance and accessibility.

Grammatically, pääreitti is the base noun; pääreittillä is the inessive/locative form meaning "on the main route." Related expressions include pääreitillä, a closely related form with the same meaning, and phrases like "pääreitin varrella" meaning along the main route. The term is commonly used in Finnish park literature, trail descriptions and logistical planning documents to distinguish the main path from side routes or detours.