The Instructive Plural Case (-in)
Finnish has a grammatical case called the instructive, which is used to describe how or by what means an action is performed. While it is rarely used to create entirely new forms on the fly today, it survives as a vital part of the language in fixed expressions of manner.
To form the instructive, attach the ending -in to the plural stem of a word. Crucially, any modifying adjective must also agree with the noun, meaning both the adjective and the noun will take the -in ending.
| Base Phrase | English | Instructive Form | English Meaning |
|---|---|---|---|
| avoin mieli | open mind | avoimin mielin | with an open mind |
| oma silmä | own eye | omin silmin | with one's own eyes |
| oma sana | own word | omin sanoin | in one's own words |
| We listened to both the teacher and the students with an open mind. | Kuuntelimme sekä opettajaa että opiskelijoita avoimin mielin. |
| I saw the accident with my own eyes, but I did not believe it. | Näin onnettomuuden omin silmin, mutta en uskonut sitä. |
| You explained both the accident and the details in your own words. | Selitit sekä onnettomuuden että yksityiskohdat omin sanoin. |
Body Parts and Intense Effort
When giving eyewitness accounts or sharing firsthand experiences, physical descriptions often rely on the instructive plural. Notice how these expressions rarely use possessive suffixes, even when referring to body parts.
Phrases like kynsin hampain (tooth and nail, literally "with nails and teeth") and kaikin voimin (with all one's might) are commonly used to describe an action done with intense effort.
| The witness held on to the bag tooth and nail. | Todistaja piti laukusta kiinni kynsin hampain. |
| Both the group and the police searched for the victim with all their might. | Sekä joukko että poliisi etsivät uhria kaikin voimin. |
| The victim escaped from the forest barefoot, without a jacket. | Uhri pakeni metsästä paljain jaloin ilman takkia. |
Adverbial Idioms
Many instructive phrases have completely fossilized into fixed adverbs of manner. Even if their literal translations feel a bit abstract—such as suurin piirtein (with large features) or ehdoin tahdoin (with terms and wills)—their figurative meanings are universally understood and used by Finnish speakers.
| The witness drank water and described the incident roughly. | Todistaja joi vettä ja kuvaili tapausta suurin piirtein. |
| He did not break the window deliberately. | Hän ei rikkonut ikkunaa ehdoin tahdoin. |
| The witness described the accident with precise details. | Todistaja kuvaili onnettomuutta tarkoin yksityiskohdin. |