Instructive -n: 'by means of / in a manner' | Finnish Grammar

The instructive is the case Finnish very nearly stopped using. Its ending is a plain -n added to the plural stem, and it means "by means of" or "in the manner of." Centuries ago it was productive; today it survives almost entirely in a closed set of fixed expressions — käsin ("by hand"), jalan ("on foot"), omin silmin ("with one's own eyes"). The single most useful thing to understand about the instructive is that you should not try to build new ones. Learn the phrases as vocabulary, and express instrument and manner the modern way — with the adessive and with -sti adverbs.

The form: plural stem + -n, and the adjective agrees

Where it does appear, the instructive attaches -n to the plural stem, so the ending is almost always -in (plural -i- + -n). The i is harmony-neutral, so you never see \-än: it is *käsin, jaloin, silmin, whatever the vowels of the stem. Crucially, an adjective in the phrase must also stand in the plural instructive.

Phrase	Literally	Meaning
jalan	by foot (sg.)	on foot
käsin	by hands	by hand
omin käsin	by own hands	with one's own hands
omin silmin	by own eyes	with one's own eyes
paljain jaloin	by bare feet	barefoot
kaikin voimin	by all forces	with all one's might
suurin piirtein	in large outlines	roughly, approximately
monin tavoin	in many ways	in many ways

Notice omin käsin, paljain jaloin, kaikin voimin: the adjective (oma, paljas, kaikki) is itself plural and instructive — omin, paljain, kaikin — matching its noun. You never mix a singular adjective with an instructive noun.

Instrument and means

The instructive's oldest job is marking the instrument or means of an action — the body part or resource you use to do something.

Tämä matto on kudottu käsin.

This rug is woven by hand.

Näin sen omin silmin.

I saw it with my own eyes.

Yritimme pelastaa sadon kaikin voimin.

We tried to save the harvest with all our might.

Jalan is the odd one out and the most common of all: it is a singular instructive fossil (identical in shape to the genitive jalan), and it means "on foot."

Menen töihin jalan.

I go to work on foot.

Manner

The instructive also marks manner — "in this/that way." A cluster of everyday adverbs is really frozen instructives, though most speakers no longer feel the case at all.

Tee se näin.

Do it like this.

Ratkaisimme ongelman monin tavoin.

We tackled the problem in many ways.

Arvioin matkan pituuden suurin piirtein.

I estimated the length of the trip roughly.

Näin ("like this"), usein ("often," historically from usea), hyvin ("well," from hyvä) and suurin piirtein are all instructive relics that have simply become ordinary adverbs. You will find more of them catalogued on adverbs from case forms.

What to use instead

Because the instructive is closed, the language expresses its two meanings productively through other means — and these are what you should actually reach for.

For a real instrument, use the adessive -lla / -llä:

Avasin oven avaimella.

I opened the door with a key.

Leikkasin leivän veitsellä.

I cut the bread with a knife.

For manner, use a -sti adverb:

Hän puhui hitaasti ja selkeästi.

He spoke slowly and clearly.

There is no productive instructive of avain ("key") or veitsi ("knife") — *avaimin, *veitsin are not how a Finn says "with a key / knife." Instrument goes to the adessive; manner goes to -sti.

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Treat the instructive as a small phrasebook, not a rule. Memorise the whole expressions — jalan, käsin, omin silmin, paljain jaloin, kaikin voimin, suurin piirtein — and never coin a new one. Need "with X"? Use the adessive (avaimella). Need "in an X way"? Use a -sti adverb (nopeasti).

A homophony to watch

The instructive -n is spelled the same as the singular genitive -n and the -n of the total object. What tells them apart is plurality and context: jaloin is unmistakably plural (it has the plural -i-), so it cannot be a genitive; jalan is singular and ambiguous in isolation (genitive "of the foot" or instructive "on foot"), but the surrounding words resolve it every time. Keep the vowel length honest, too: it is käsin, jaloin, silmin — clipping or lengthening the vowel changes or breaks the word.

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If an adjective sits before an instructive noun, it must copy the ending: omin käsin, paljain jaloin, kaikin voimin — never *oma käsin or *paljas jaloin. Both words go plural, both take -in.

Common Mistakes

❌ Näin sen oma silmin.

Incorrect — the adjective must agree in the plural instructive: omin.

✅ Näin sen omin silmin.

I saw it with my own eyes.

❌ Menen töihin jalalla.

Incorrect — 'on foot' is the fixed instructive jalan; jalalla means 'with a foot'.

✅ Menen töihin jalan.

I go to work on foot.

❌ Leikkasin leivän veitsin.

Incorrect — for a real instrument use the adessive, not a coined instructive: veitsellä.

✅ Leikkasin leivän veitsellä.

I cut the bread with a knife.

❌ Kävelin rannalla paljas jaloin.

Incorrect — the adjective must be plural instructive too: paljain.

✅ Kävelin rannalla paljain jaloin.

I walked on the beach barefoot.

❌ Hän puhui kaunis tavoin.

Incorrect — manner is normally a -sti adverb: kauniisti.

✅ Hän puhui kauniisti.

He spoke beautifully.

Key Takeaways

The instructive -n (usually -in, on the plural stem) means "by means of / in a manner" and is not productive — it lives in a closed set of fixed phrases.
Learn them whole: käsin, jalan (on foot), omin silmin, paljain jaloin, kaikin voimin, suurin piirtein, monin tavoin, näin.
Adjectives in these phrases agree — both words plural, both in -in: omin käsin, paljain jaloin.
Produce instrument with the adessive (avaimella) and manner with a -sti adverb (hitaasti); do not invent new instructives.
The ending is homophonous with the genitive/object -n; plurality and context disambiguate.

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