The Fifth Infinitive -maisillaan | Finnish Grammar

The fifth infinitive is the rarest and most stylistically marked of the set — a single, tightly frozen construction that means "on the very verge of doing" something that then, typically, does not happen. It ends in -maisilla-/-mäisillä- and always carries a possessive suffix: kuolemaisillaan ("about to die"), lähtemäisilläni ("about to leave," of me). You will meet it in novels, news headlines and dramatic narration far more than in speech, but it is unmistakable and worth being able to read.

Form: -ma- stem + -isilla- + possessive

Take the third infinitive's -ma-/-mä- stem (built on the strong present stem, see the third infinitive overview), add -isilla-/-isillä-, and finish with an obligatory possessive suffix that agrees with the subject. The stem is historically the adessive plural of an adjective -mainen, which is why the possessive is not optional — the word literally cannot stand without it.

Subject	olla + fifth infinitive (lähteä)	Meaning
minä	olin lähtemäisilläni	I was about to leave
sinä	olit lähtemäisilläsi	you were about to leave
hän	oli lähtemäisillään	he/she was about to leave
me	olimme lähtemäisillämme	we were about to leave
te	olitte lähtemäisillänne	you (pl.) were about to leave
he	olivat lähtemäisillään	they were about to leave

Three spelling points, all non-negotiable:

Harmony fixes -illaan vs. -illään: a back-vowel verb gives kaatumaisillaan, a front-vowel verb gives tekemäisillään.
Gradation stays strong, just as in the third infinitive: tehdä → tekemäisillään (with k), never *teemäisillään.
The possessive suffix is mandatory. There is no bare *kuolemaisilla; the third person is kuolemaisillaan.

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Break the word into pieces and it stops being frightening: kuole- (stem of kuolla) + -maisilla- ("on the brink-ness") + -an ("his/her"). Every fifth infinitive is built the same way, so once you can parse one, you can parse them all.

Meaning: imminent, not yet realised

The fifth infinitive marks an action poised to happen but not (yet) happening — the split second before the event. This is different from a perfective "nearly did," which Finnish expresses with melkein + a finite verb: melkein kuolin ("I nearly died," a completed near-miss) reports an event that came close, whereas olin kuolemaisillani freezes the frame on the brink, describing the teetering state itself. English blurs these two into one "about to / nearly"; Finnish keeps them apart. The fifth infinitive almost always appears with olla ("to be").

Hän oli kuolemaisillaan, kun apu vihdoin saapui.

He was on the verge of death when help finally arrived.

Vanha silta on romahtamaisillaan.

The old bridge is about to collapse.

Olin nukahtamaisillani, kun puhelin soi.

I was on the point of dozing off when the phone rang.

A handful of verbs account for most real occurrences — the construction is close to lexicalised with them. Learn these as set pieces:

Verb	Fifth infinitive (3rd person)	Meaning
kuolla	kuolemaisillaan	about to die
kaatua	kaatumaisillaan	about to fall over
nukahtaa	nukahtamaisillaan	about to doze off
itkeä	itkemäisillään	about to cry
pyörtyä	pyörtymäisillään	about to faint

Lapsi oli itkemäisillään, kun jäätelö putosi maahan.

The child was about to cry when the ice cream fell on the ground.

Hän horjahti ja oli kaatumaisillaan portaissa.

She stumbled and was about to fall on the stairs.

Kuumuudessa moni oli pyörtymäisillään.

In the heat many were on the point of fainting.

Almost always third person — and mostly literary

Because the fifth infinitive lives in narration ("he was about to…"), it appears overwhelmingly in the third person and in (literary) register. In everyday speech Finns do not build it on the fly; they reach for plainer constructions instead:

olla + -massa — olin juuri lähtemässä ("I was just leaving / about to leave"), the neutral, colloquial choice;
olla lähdössä / tulossa — a -ssa action-noun, very common in speech;
aikoa — aioin juuri lähteä ("I was just going to leave").

Olin juuri lähtemässä, kun sinä soitit.

I was just about to leave when you called.

Ai, sinäkin olet lähdössä? Mennään yhdessä.

Oh, you're leaving too? Let's go together.

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Treat the fifth infinitive as read-not-write vocabulary until you're advanced. For "about to" in conversation, olla lähdössä or olla juuri tekemässä is what a native speaker actually says; reserve -maisillaan for dramatic or written Finnish, or you'll sound like a nineteenth-century novel.

Don't confuse it with the third infinitive -massa

Both forms can translate as "about to," but they are not interchangeable. -massa frames the action as ongoing / just-starting and is register-neutral; -maisillaan frames it as teetering on the very edge and is emphatic and literary. Olin lähtemässä is a calm "I was leaving"; olin lähtemäisilläni is a charged "I was this close to leaving." See olla uses for how olla anchors both.

Common Mistakes

❌ Hän oli kuolemaisilla.

Incorrect — the possessive suffix is obligatory; the third person is kuolemaisillaan.

✅ Hän oli kuolemaisillaan.

He was about to die.

❌ Olin teemäisilläni lähtemään.

Incorrect — gradation stays strong (tekemäisilläni), and the construction takes no extra infinitive.

✅ Olin tekemäisilläni virheen.

I was about to make a mistake.

❌ Olen lähtemäisilläni kauppaan hakemaan maitoa, tuutko?

Odd register — for an everyday 'about to', use olla lähdössä / olla lähtemässä instead.

✅ Olen lähdössä kauppaan, tuutko mukaan?

I'm about to head to the shop, are you coming along?

❌ Silta on romahtamaisillään.

Incorrect — romahtaa is a back-vowel verb, so harmony gives -illaan, not -illään.

✅ Silta on romahtamaisillaan.

The bridge is about to collapse.

Key Takeaways

The fifth infinitive = -ma- stem + -isilla-/-isillä- + obligatory possessive: kuolemaisillaan, lähtemäisilläni.
It means "on the very verge of" an action that hasn't happened yet, and it pairs with olla.
It is third-person and (literary) in practice, frozen around a few verbs (kuolla, kaatua, nukahtaa).
For everyday "about to," use olla lähdössä, olla -massa, or aikoa — not this form.
Harmony picks -illaan/-illään; gradation stays strong; the possessive can never be dropped.

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