Learn Finnish: Sen sijaan että rehtori edistää kuria, hän rankaisee opettajia. - Instead of promoting discipline, the principal punishes the teachers.

English says "instead of promoting", but Finnish postpositions like sijaan cannot attach directly to an että clause. We use the pronoun se as a bridge. Because sijaan requires a genitive modifier, se becomes sen. The full bridge is sen sijaan, which then points forward to the että clause.

Why does the Finnish sentence say että rehtori edistää instead of using a verb form like "promoting"?

Finnish doesn't use an "-ing" equivalent after "instead of" in this structure. Because we are using an että (that) clause, it must be a complete sentence with its own subject (rehtori) and a fully conjugated verb (edistää). Literally, it translates to "Instead of it that the principal promotes...".

Why is the object kuria in the partitive case?

The verb edistää (to promote or advance) describes an ongoing process or abstract action rather than a concrete action with a finished endpoint. Verbs of this nature require their object to be in the partitive case, so kuri (discipline) becomes kuria.

Why is opettajia (teachers) in the partitive plural instead of the accusative?