In Part 1, we covered the noun types where the stem is fairly predictable. Once you know the type, you can often guess the inflected forms.

This part is different.

The types below have stems that change shape so much that you simply have to learn them. There’s no shortcut — guessing won’t work, and getting them wrong is one of the most common mistakes learners make at A1–A2 level.

The good news: once you’ve learned the pattern for each type, you’ll recognise it instantly in every new word.

Type 7 — -IS / -AS Sanat (Words Ending in -IS or -AS)

Ending: -is or -as

Examples: kaunis (beautiful), asiakas (customer), arvokas (valuable), kallis (expensive)

This type changes a lot between the dictionary form and the stem. The ending vowel lengthens, and the final consonant disappears or changes shape.

Key facts:

• Stem: -is → -ii-, -as → -aa- (kaunis → kaunii-, asiakas → asiakkaa-)
• Partitive: if the word ends in a single consonant, add -ta/-tä directly to the dictionary form → kaunista, asiakasta
• KPT: weak → strong (Group B)

Form	kaunis	asiakas	arvokas
Dictionary	kaunis	asiakas	arvokas
Stem	kaunii-	asiakkaa-	arvokkaa-
Genetiivi (-n)	kauniin	asiakkaan	arvokkaan
Partitiivi	kaunista	asiakasta	arvokasta
Inessiivi (-ssa)	kauniissa	asiakkaassa	arvokkaassa
Illatiivi	kauniiseen	asiakkaaseen	arvokkaaseen

KPT example: asiakas → stem is asiakkaa- (k → kk, weak to strong). The dictionary form is weak; the stem is strong.

kallis (expensive) follows the same pattern: stem kallii-

→ Minä asun kalliissa talossa. (I live in an expensive house.)

Common words in this type: kaunis, kallis, asiakas, arvokas, raskas, rikas…

Type 8 — -US / -OS / -YS / -ÖS Sanat (Words Ending in -US, -OS, -YS, -ÖS)

Ending: -us, -os, -ys, -ös

Examples: kerros (floor/layer), varaus (reservation), kysymys (question), käännös (translation)

This type adds -kse- into the stem — a clear and consistent marker once you learn to recognise it.

Key facts:

• Stem: -os/-us/-ys/-ös → -okse-/-ukse-/-ykse-/-ökse- (kerros → kerrokse-)
• Partitive: add -ta/-tä directly to the dictionary form if it ends in a consonant → kerrosta
• KPT: usually no change in the consonant itself — the -kse- insertion is the main feature

Form	kerros	kysymys
Dictionary	kerros	kysymys
Stem	kerrokse-	kysymykse-
Genetiivi (-n)	kerroksen	kysymyksen
Partitiivi	kerrosta	kysymystä
Inessiivi (-ssa)	kerroksessa	kysymyksessä
Illatiivi	kerrokseen	kysymykseen

Common words in this type: kerros, kysymys, vastaus, varaus, varoitus, valmennus …

Irregular exception: words ending in -uus/-yys (like rakkaus, kauneus) behave a bit differently — they follow the old -si pattern instead (-de- stem), not -kse-. Learn these separately.

Crossover words: some -is and -as words borrow this -kse- pattern instead of the regular Type 7 pattern: kasvis → kasvikse-, varis → varikse-, ananas → ananakse-. There’s no way to predict this — you simply need to learn these specific words.

Type 9 — -IN Sanat (Words Ending in -IN)

Ending: -in

Examples: avain (key), puhelin (phone), kahvinkeitin (coffee maker), puristin (pressing device)

The -in ending becomes -ime- in the stem — a small but important shift.

Key facts:

• Stem: -in → -ime- (avain → avaime-, puhelin → puhelime-)
• Partitive: add -ta/-tä directly to the dictionary form → avainta, puhelinta
• KPT: weak → strong (Group B)

Form	avain	puhelin	kahvinkeitin
Dictionary	avain	puhelin	kahvinkeitin
Stem	avaime-	puhelime-	kahvinkeittime-
Genetiivi (-n)	avaimen	puhelimen	kahvinkeittimen
Partitiivi	avainta	puhelinta	kahvinkeitintä
Inessiivi (-ssa)	avaimessa	puhelimessa	kahvinkeittimessä
Illatiivi	avaimeen	puhelimeen	kahvinkeittimeen

KPT example: kahvinkeitin → stem kahvinkeittime- (t → tt, weak to strong).

Common words in this type: avain, puhelin, kahvinkeitin, vatkain (mixer),

Type 10 — -TON / -TÖN Sanat (Words Ending in -TON/-TÖN)

Ending: -ton, -tön (a very productive adjective ending meaning ”without”)

Examples: sokeriton (sugar-free), levoton (restless), työtön (unemployed)

This is one of the most common adjective endings in Finnish — and very useful, because you can attach it to almost any noun to mean ”without ___”.

Key facts:

• Stem: -ton/-tön → -ttoma-/-ttömä- (sokeriton → sokerittoma-)
• Partitive: add -ta/-tä directly to the dictionary form → sokeritonta
• KPT: weak → strong (Group B)

Form	sokeriton	levoton	työtön
Dictionary	sokeriton	levoton	työtön
Stem	sokerittoma-	levottoma-	työttömä-
Genetiivi (-n)	sokerittoman	levottoman	työttömän
Partitiivi	sokeritonta	levotonta	työtöntä
Inessiivi (-ssa)	sokerittomassa	levottomassa	työttömässä
Illatiivi	sokerittomaan	levottomaan	työttömään

Why this matters: -ton/-tön is extremely productive. You can build new words on the spot: lapseton (childless), kodittomat (homeless people), maksuton (free of charge). Learning the stem pattern once means you can handle all of them.

Common words in this type: työtön, sokeriton, levoton, maksuton, koditon, lapseton, rajaton

Type 11 — -NSI / -RSI Sanat (Words Ending in -NSI or -RSI)

Ending: -si, with a consonant (n or r) right before it

Examples: kansi (lid), kynsi (nail/claw), varsi (handle/stem), länsi (west)

These are less common than the other types, but they appear in everyday vocabulary, so they’re worth knowing. The ending changes dramatically: the consonant doubles and the -si disappears.

Key facts:

• Stem: -nsi → -nne-, -rsi → -rre- (kansi → kanne-, varsi → varre-)
• Partitive: -nsi → -ntta/-nttä, -rsi → -rtta/-rttä (kansi → kantta, varsi → vartta)
• Illative: -nsi → -nteen, -rsi → -rteen (kansi → kanteen, varsi → varteen)
• KPT: weak → strong (Group B)

Form	kansi	varsi	länsi
Dictionary	kansi	varsi	länsi
Stem	kanne-	varre-	länne-
Genetiivi (-n)	kannen	varren	lännen
Partitiivi	kantta	vartta	länttä
Inessiivi (-ssa)	kannessa	varressa	lännessä
Illatiivi	kanteen	varteen	länteen

Tip: this type is small — there aren’t many words that follow it. Once you’ve learned kansi, kynsi, varsi, länsi, you’ve covered most of the common ones.

Common words in this type: kansi, kynsi, varsi, länsi

Quick Recognition Guide — Part 2 Types

Ending	Type	Stem change	Example
-is / -as	IS/AS-sanat	-ii-/-aa-	kaunis → kaunii-
-us/-os/-ys/-ös	US/OS-sanat	-kse- inserted	kerros → kerrokse-
-in	IN-sanat	-in → -ime-	avain → avaime-
-ton/-tön	TON-sanat	-ttoma-/-ttömä-	sokeriton → sokerittoma-
-nsi/-rsi	NSI/RSI-sanat	-nne-/-rre-	kansi → kanne-

Why These Types Are Worth the Effort

These five types are common in everyday vocabulary, adjectives, and especially in formal or written Finnish — job descriptions, news articles, official letters. If you’re preparing for YKI or just want to read Finnish confidently, these patterns will keep showing up.

The trick isn’t to memorise hundreds of words. It’s to recognise the ending, and then test the stem by trying to put the word into a sentence with -ssa (in) or -lla (with). If it sounds wrong, you’ve probably got the wrong stem — go back and check the pattern.

PRACTICE TIME!