Finnish stems (vartalo)

The genitive (genetiivi, -n) is the key form: it shows the stem that all the other cases use. Look at the ending of the basic form, find the rule, build the stem – derive instead of memorising.

The colour shows which kind of stem results: vowel stem, weak grade · stem with strong grade · consonant stem. The underlined part is the part that changes. Finnish has no grammatical gender; what matters is the stem type.

Overview

Rule	Basic form ends in	Genitive stem	Example	Reliability
nen	-nen	-se-	nainen → naisen (woman)	always
in	-in	-ime-	puhelin → puhelimen (telephone)	always
ton	-ton / -tön	-ttoma- / -ttömä-	työtön → työttömän (unemployed)	always
as	-as / -äs	-aa- / -ää-, strong grade	asiakas → asiakkaan (customer)	always
uus	-uus / -yys	-uude- / -yyde-	ahkeruus → ahkeruuden (diligence)	always
us_ude	-us / -ys (quality nouns)	-ude- / -yde-	rakkaus → rakkauden (love (rakas, dear))	almost always
us	-us / -ys (other)	-ukse- / -ykse-	ajatus → ajatuksen (thought)	almost always
os	-os / -ös	-okse- / -ökse-	kerros → kerroksen (floor, storey)	always
is	-is (nouns)	-ikse-	jänis → jäniksen (hare)	for nouns
e	-e	-ee-, strong grade	huone → huoneen (room)	almost always
si	-si	-de- (or -re-, -ne-, -le-, -kse-, -pse-, -tse-)	käsi → käden (hand)	native words, always
i_old	-i (old word)	-e-, weak grade	nimi → nimen (name)	old native words, closed list
i_new	-i (new word)	-i-, weak grade	bussi → bussin (bus)	almost always
vowel	-a/-ä, -o/-ö, -u/-y, -ie/-ee	unchanged, weak grade	talo → talon (house)	always, the default case

Order of checking: the longer, more specific endings come first (-nen, -in, -ton, -as, -uus, -os, -is, -us, -si), then -e, then -i (old list or new word); a vowel ending is the default case. Compounds follow their last part.

⚠ Some common words follow no rule and are learnt together with their genitive: mies → miehen (man), veli → veljen (brother), tytär → tyttären (daughter), kevät → kevään (spring), sydän → sydämen (heart), jäsen → jäsenen (member), koe → kokeen (exam).

-nen → -se-

Ending: words in -nen: nouns and adjectives (suomalainen, Finnish).

Stem and genitive: -nen becomes -se-: the genitive stem ends in -se, followed by -n.

Basic form	Genitive	English
nainen	naisen	woman
ihminen	ihmisen	human being
hevonen	hevosen	horse
lautanen	lautasen	plate
aamiainen	aamiaisen	breakfast
kansalainen	kansalaisen	citizen

Reliability: always. No consonant gradation.

-in → -ime-

Ending: longer words in -in, mostly tools and devices (five letters or more).

Stem and genitive: -in becomes -ime-.

Basic form	Genitive	English
puhelin	puhelimen	telephone
avain	avaimen	key
eläin	eläimen	animal
luistin	luistimen	ice skate
tulostin	tulostimen	printer

Reliability: always.

⚠ Device names derived from a verb with consonant gradation have the strong grade in the stem: soitin → soittimen (instrument; verb soittaa), palovaroitin → palovaroittimen (smoke detector). The drill does not cover this yet.

-ton / -tön → -ttoma- / -ttömä-

Ending: adjectives in -ton / -tön mean without, like German -los.

Stem and genitive: -ton becomes -ttoma-, -tön becomes -ttömä- (vowel harmony).

Basic form	Genitive	English
työtön	työttömän	unemployed
rahaton	rahattoman	without money, broke
onneton	onnettoman	unhappy
koditon	kodittoman	homeless

Reliability: always. The tt is already in the stem, so there is no consonant gradation to apply.

-as / -äs → -aa- / -ää-, strong grade

Ending: words in -as / -äs after a consonant.

Stem and genitive: -as becomes -aa-, and the consonant before it takes the strong grade: the basic form has the weak one (hammas: mm), the genitive brings back the strong one (hampaan: mp). See consonant gradation (astevaihtelu).

Basic form	Genitive	English
asiakas	asiakkaan	customer
hammas	hampaan	tooth
kangas	kankaan	fabric
taivas	taivaan	sky
potilas	potilaan	patient
tehdas	tehtaan	factory

Reliability: always.

⚠ the -as that is really -kse-: lihas → lihaksen (muscle), teräs → teräksen (steel). ⚠ varas → varkaan (thief, r/rk). Adjectives in -as often behave like nouns (rakas → rakkaan, dear).

-uus / -yys → -uude- / -yyde-

Ending: abstract nouns with a long vowel: -uus / -yys (German -keit, -heit).

Stem and genitive: -uus becomes -uude-, -yys becomes -yyde-.

Basic form	Genitive	English
ahkeruus	ahkeruuden	diligence
kylmyys	kylmyyden	coldness
hauskuus	hauskuuden	fun
köyhyys	köyhyyden	poverty
mahdollisuus	mahdollisuuden	possibility
etäisyys	etäisyyden	distance

Reliability: always.

-us / -ys (quality nouns) → -ude- / -yde-

Ending: quality nouns derived from an adjective (or a short noun) with a single vowel -us / -ys: rakas → rakkaus, terve → terveys. Also korkeus (height), rohkeus (courage), leveys (width), talous (economy), yhteys (connection), kateus (envy), varkaus (theft).

Stem and genitive: -us becomes -ude-, -ys becomes -yde-. Same genitive as for -uus, but the basic form has only one vowel.

Basic form	Genitive	English
rakkaus	rakkauden	love (rakas, dear)
terveys	terveyden	health (terve, healthy)
vapaus	vapauden	freedom (vapaa, free)
oikeus	oikeuden	right (oikea, correct)
sairaus	sairauden	illness (sairas, ill)
nopeus	nopeuden	speed (nopea, fast)

Reliability: almost always – but you have to recognise the word as a quality noun. Test: can you strip the ending so that an adjective is left (rakas, terve, vapaa)? Then -ude- applies. If the base is a verb (ajatella → ajatus), -ukse- applies. Both look the same: sairaus (from the adjective sairas) → sairauden, but vastaus (from the verb vastata) → vastauksen.

-us / -ys (other) → -ukse- / -ykse-

Ending: the normal case: -us / -ys that are not quality nouns. Typical are -tus / -tys, -mus / -mys, derived from a verb (ajatella → ajatus), and also -us after a consonant (hius → hiuksen, hair).

Stem and genitive: -us becomes -ukse-, -ys becomes -ykse-.

Basic form	Genitive	English
ajatus	ajatuksen	thought
kysymys	kysymyksen	question
vastaus	vastauksen	answer
kokous	kokouksen	meeting
harjoitus	harjoituksen	exercise
koulutus	koulutuksen	training, education

Reliability: almost always. Unsure between -ukse- and -ude-? Derived from a verb or ending in -tus/-tys/-mus/-mys: -ukse-. Derived from an adjective (single vowel before -s): -ude-.

⚠ the quality nouns in -ude-.

-os / -ös → -okse- / -ökse-

Ending: words in -os / -ös (four letters or more).

Stem and genitive: -os becomes -okse-, -ös becomes -ökse-.

Basic form	Genitive	English
kerros	kerroksen	floor, storey
päätös	päätöksen	decision
tulos	tuloksen	result
muutos	muutoksen	change
kiitos	kiitoksen	thanks
rikos	rikoksen	crime

Reliability: always.

-is (nouns) → -ikse-

Ending: nouns in -is after a consonant.

Stem and genitive: -is becomes -ikse-.

Basic form	Genitive	English
jänis	jäniksen	hare
roskis	roskiksen	rubbish bin
tennis	tenniksen	tennis

Reliability: for nouns. Adjectives in -is behave differently.

⚠ Adjectives: kaunis → kauniin (beautiful). ⚠ metsäkauris → metsäkauriin (roe deer).

-e → -ee-, strong grade

Ending: nouns in -e (also -ue: alue, joukkue).

Stem and genitive: -e becomes -ee-, and the consonant before it takes the strong grade (eläke → eläkkeen, sade → sateen). Words without consonant gradation just double the vowel (huone → huoneen). See consonant gradation (astevaihtelu).

Basic form	Genitive	English
huone	huoneen	room
perhe	perheen	family
kirje	kirjeen	letter
eläke	eläkkeen	pension
osoite	osoitteen	address
sade	sateen	rain

Reliability: almost always.

⚠ nukke → nuken (doll: double consonant, weak grade as with -o, -a). ⚠ kylpyamme → kylpyammeen (bathtub). ⚠ pyyhe → pyyhkeen (towel, h/hk).

-si → -de- (or -re-, -ne-, -le-, -kse-, -pse-, -tse-)

Ending: native words in -si (not -ssi, which is a loanword).

Stem and genitive: mostly -si becomes -de- (käsi → käden). After r, n, l the s assimilates: -rsi → -rre-, -nsi → -nne-, -lsi → -lle-. After k, p, t the s stays: -ksi → -kse-, -psi → -pse-, -tsi → -tse- (lapsi → lapsen, veitsi → veitsen).

Basic form	Genitive	English
käsi	käden	hand
vesi	veden	water
vuosi	vuoden	year
lapsi	lapsen	child
käsivarsi	käsivarren	arm
länsi	lännen	west

Reliability: native words, always. Likewise susi → suden (wolf), liesi → lieden (stove).

⚠ kuusi → kuusen (spruce). ⚠ Loanwords and words with a long vowel stay unchanged, see -i stays: riisi → riisin (rice), taksi → taksin, keksi → keksin, kriisi → kriisin.

-i (old word) → -e-, weak grade

Ending: a closed list of about fifty old native words in -i.

Stem and genitive: -i becomes -e- with the weak grade (lehti → lehden, joki → joen).

Basic form	Genitive	English
nimi	nimen	name
kieli	kielen	language
ovi	oven	door
joki	joen	river
lehti	lehden	leaf
lampi	lammen	pond

Reliability: old native words, a closed list. You cannot tell them from their form: the list has to be learnt. Every -i word that is not on it keeps its -i (next section).

The list (compounds follow their last part: etunimi → etunimen, sanomalehti → sanomalehden):

nimi, kieli, ovi, lumi, talvi, meri, järvi, joki, vuori, saari, hiiri, suomi, sormi, tuuli, onni, nuori, uni, veri, kivi, lehti, tähti, pilvi, hetki, huoli, retki, tuli, arki, polvi, sieni, vuohi, hanhi, hiili, hirvi, tammi, juuri, lampi, happi, järki, juoni, putki, tiili

Consonant gradation shows in: lehti → lehden, tähti → tähden, joki → joen, lampi → lammen, happi → hapen, arki → arjen, järki → järjen. Not in hetki → hetken, putki → putken, retki → retken (tk never changes grade).

-i (new word) → -i-, weak grade

Ending: every other word in -i: loanwords (hotelli, kahvi, lääkäri) and the native words that are not on the old list (äiti, täti, tuoli, lasi).

Stem and genitive: -i stays; -n is added. Only the weak grade applies (pankki → pankin, tunti → tunnin, äiti → äidin). Words ending in a diphthong (-ai, -oi) never have consonant gradation.

Basic form	Genitive	English
bussi	bussin	bus
pankki	pankin	bank
kaupunki	kaupungin	town, city
tunti	tunnin	hour
äiti	äidin	mother
maanantai	maanantain	Monday

Reliability: almost always: the default case for -i, unless the word is on the old list.

⚠ the old words with -i → -e- and the native -si words.

-a/-ä, -o/-ö, -u/-y, -ie/-ee → unchanged, weak grade

Ending: words that end in a vowel other than -e / -i: -a/-ä, -o/-ö, -u/-y, as well as the long endings -ie, -ee (tie, maa, yö, työ).

Stem and genitive: the stem is the basic form; -n is added. If the basic form has a strong consonant, it becomes weak (katu → kadun, kuva → kuvan). See consonant gradation (astevaihtelu).

Basic form	Genitive	English
talo	talon	house
katu	kadun	street
tyttö	tyttön	girl
poika	pojan	boy
pöytä	pöydän	table
tie	tien	road, way

Reliability: always, the default case. If nothing else fits, this rule applies.

⚠ Words that ought to have consonant gradation but do not (mostly newer or borrowed ones): pipo → pipon (beanie, not pivon), auto → auton, tipu → tipun (chick), paprika → paprikan. ⚠ hk: mostly no consonant gradation (sähkö → sähkön, keuhko → keuhkon), but vihko → vihon (exercise book).

Rules as implemented in the drill (data/fi/stem_rules.json); every example is a word from the dictionary, except the -ton words and the additional exceptions named in the notes.