Finnish is famous for having "fifteen cases," but that headline number hides a truth: the cases are not equally alive. The core grammatical cases — nominative, genitive, partitive (and the accusative) — together with the six local cases carry the everyday grammatical load; then come a handful of marginal cases that range from fully productive to almost fossilized. This page is a map of that tail end — a single place to see the essive, translative, abessive, comitative and instructive side by side, plus the borderline fifteenth case, the prolative -tse, which is why grammarians argue about whether the count is fourteen or fifteen. Use it as a reference and a triage guide: what to learn to produce, and what merely to recognise.
The marginal cases at a glance
| Case | Ending | Function | Example | Status |
|---|---|---|---|---|
| Essive | -na / -nä | being in a state | lääkärinä (as a doctor) | alive, common |
| Translative | -ksi | changing into a state | lääkäriksi (into a doctor) | alive, common |
| Abessive | -tta / -ttä | without | rahatta (without money) | noun: literary; verb -matta: alive |
| Comitative | -ine- + poss. | accompanied by | puolisoineen (with a spouse) | formal / literary |
| Instructive | -n (plural) | by means of / in a manner | omin käsin (with own hands) | frozen phrases only |
| Prolative | -tse | via / by way of | postitse (by post) | semi-productive |
The essive and translative are ordinary tools you use daily — they earn their own pages and the state-vs-change chooser is where their contrast is drawn. The abessive is half-alive: dead as a noun ending in speech, but thriving as the verbal -matta / -mättä. The comitative and instructive are, respectively, elegantly formal and effectively frozen. And then there is the prolative.
The prolative -tse: the borderline case
The prolative marks a route or medium — the "via" or "by way of" through which something travels. It attaches -tse to the inflectional stem and, like several marginal endings, never harmonises: it is always -tse, whatever the stem's vowels.
| Word | Stem | Prolative | Meaning |
|---|---|---|---|
| posti (post) | posti- | postitse | by post |
| puhelin (telephone) | puhelime- | puhelimitse | by phone |
| sähköposti (email) | sähköposti- | sähköpostitse | by email |
| meri (sea) | mere- | meritse | by sea |
| maa (land) | maa- | maitse | by land |
| rautatie (railway) | rautatie- | rautateitse | by rail |
Watch the stem: puhelin becomes puhelime- before the ending, giving puhelimitse — not *puhelintse. The prolative reaches for the inflectional stem, exactly like the other cases.
Lähetän asiakirjat postitse.
I'll send the documents by post.
Ilmoittautuminen tapahtuu puhelimitse tai sähköpostitse.
Registration is done by phone or email.
Tavarat kuljetetaan meritse.
The goods are transported by sea.
Rajan yli pääsee vain maitse.
You can cross the border only by land.
The prolative is called semi-productive because it is not fully closed — new forms turn up for media and channels (you will even hear the (informal) netitse, "online") — but it is almost always replaceable by kautta ("via") or an adessive, which is why it sits on the edge of the case system.
Ota yhteyttä puhelimitse.
Get in touch by phone. (or, more colloquially: puhelimella / soittamalla)
Lähetän sen postin kautta.
I'll send it via the post. (the everyday paraphrase of postitse)
How the three cases divide "with / by"
Because English lumps them together under "with" and "by," it is worth lining up the three that a learner most often confuses. They are not interchangeable:
- Comitative = accompaniment — someone/something comes along: lapsineen ("with his children").
- Instructive = means/manner — the tool or way an action is done: omin käsin ("by hand").
- Prolative = route/medium — the channel something travels through: postitse ("by post").
Presidentti saapui puolisoineen.
The president arrived with his spouse. (comitative — accompaniment)
Kutsu lähetettiin sähköpostitse.
The invitation was sent by email. (prolative — medium)
Even more marginal: lexicalized relics
Below the prolative lies a layer of endings that are no longer cases at all — they survive only inside individual frozen words. The old lative ending shows up in direction adverbs like ulos ("out"), alas ("down") and kauas ("far"); scattered essive and instructive relics have hardened into everyday adverbs like ensin ("first"), ulkona ("outside") and näin ("thus"). These are not something to inflect; they are vocabulary with a history. They are gathered on rare and relic forms and adverbs from case forms.
Common Mistakes
❌ Lähetän sen postitsen.
Incorrect — the prolative ending is invariant -tse, with no added -n.
✅ Lähetän sen postitse.
I'll send it by post.
❌ Otan yhteyttä puhelintse.
Incorrect — the ending attaches to the stem puhelime-, giving puhelimitse.
✅ Otan yhteyttä puhelimitse.
I'll get in touch by phone.
❌ Tavara kulki meren kautta meritse.
Incorrect — use one route marker, not both; kautta and -tse do the same job.
✅ Tavara kulki meritse.
The goods travelled by sea.
❌ Hän lähti perheine.
Incorrect — the comitative needs a possessive suffix: perheineen.
✅ Hän lähti perheineen.
He left with his family.
❌ Näin sen oma silmin.
Incorrect — the instructive adjective must agree in the plural: omin.
✅ Näin sen omin silmin.
I saw it with my own eyes.
Key Takeaways
- Finnish's "fifteen cases" thin out into a tail of marginal cases that differ sharply in how alive they are.
- Alive and productive: essive -na/-nä, translative -ksi, and the verbal abessive -matta/-mättä.
- Recognise, don't build: the noun abessive -tta (literary), the comitative -ine- (formal), and the instructive -n (frozen phrases).
- The prolative -tse ("via / by way of": postitse, meritse, puhelimitse) is the borderline fifteenth case — semi-productive, never harmonising, and nearly always replaceable by kautta or an adessive.
- Distinguish the three "with/by" cases: comitative = accompaniment, instructive = means/manner, prolative = route/medium.
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Start learning Finnish→Related Topics
- Instructive -n: 'by means of / in a manner'C1 — The instructive plural -n survives in frozen phrases — jalan, käsin, omin silmin, paljain jaloin — meaning 'by means of' or 'in a way'; it is not productive.
- Comitative -ine-: 'with (accompanied by)'C1 — The comitative -ine- means 'accompanied by' — always plural in shape, always with a possessive suffix (lapsineen); everyday Finnish uses kanssa instead.
- Rare and Frozen Case FormsC2 — Lexicalized case relics that survive as adverbs and set phrases — kotona, aamuisin, omin käsin, ulos, luona — memorized whole rather than built from living cases.
- Frozen Case Forms as AdverbsB1 — Many Finnish adverbs are old nouns frozen in one case — kotona/kotiin/kotoa, ulos, onneksi, jalan — learned whole and never re-inflected.