Instructive phrases (-in)

The instructive case is used to describe the manner or means by which an action is performed. It often translates to "with" or acts as an adverb in English.

Forming the Instructive Case

The instructive case is almost exclusively used in the plural. You form it by adding the suffix -n to the noun's plural stem, which means the ending will always appear as -in (the plural marker -i- plus the instructive -n).

Crucially, when a noun is modified by an adjective, both the adjective and the noun take the -in ending. This creates vivid, fixed descriptive phrases.

Body Parts and Physical Exertion

A very common use of the instructive case is describing actions done using specific body parts, or describing physical exertion. Notice how both words in phrases like paljain jaloin (with bare feet / barefoot) or kaikin voimin (with all our might) take the -in suffix.

Manner and Movement

You will also use these adjectival phrases to describe the specific manner of movement or the conditions under which something happens.

Idiomatic and Abstract Phrases

The instructive case forms many fixed idioms, often using abstract nouns like mieli (mind), määrä (amount), or physical concepts like syli (arms/lap) or suu (mouth) applied metaphorically. These phrases function as strong adverbs in a sentence, such as doing something "confidently" (luottavaisin mielin) or "headlong" (suin päin).