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Vowel Harmony – Vokaaliharmonia – Finnish Grammar

Vowel harmony, in Finnish vokaaliharmonia or vokaalisointu, is something that influences every verb and noun that you conjugate or inflect. It influences the vowels, aka A, E, I, O, U, Y, Ä and Ö.

1. The Basic Rule

In Finnish, you can divide the vowels in two main groups. In general, inside one word, you will only find vowels from one group OR from the other group. The two groups of vowels don’t normally mix.

  • The vowels A, O and U form one group. You can see these vowels in the words auto, poolo, hullu, laulu, toukka, and aamu.
  • The vowels Ä, Ö and Y form another group. You can find these vowels in the words tyttö, hylly, pöllö, t, mäyrä, käytävä, and mhässä.

This leaves us with the vowels E and I. They can appear in words by their own: kieli, tie, liesi, tee, tiimi. However, the vowels E and I are often called “neutral vowels”. This is because they can appear inside words:

  • with A, O and Utuoli, piano, poliisi, teema, tietokone
  • with Ä, Ö and Y — ääliö, tyyli, seinä, kehä, kynsi, yleisö

2. Vowel Harmony when Words Change

The words above all are in their basic form. However, vowel harmony reaches much further than that. The suffixes you add to the end of words when inflecting or conjugating them will also need to abide by the vowel harmony rules.

Some examples of noun forms

Basic Partitive Inessive (missä) Elative (mistä) Explanation
kuuma kuumaa kuumassa kuumasta word containing the vowels AOU gets -a
koulu koulua koulussa koulusta word containing the vowels AOU, gets -a
tuoli tuolia tuolissa tuolista word containing the vowels AOU, gets -a
hylly hyllyä hyllyssä hyllystä word without the vowels AOU, gets -ä
pöllö pöllöä pöllössä pöllöstä word without the vowels AOU, gets -ä
kivääri kivääriä kiväärissä kivääristä word without the vowels AOU, gets -ä
sieni sientä sienessä sienestä word without the vowels AOU, gets -ä

Some examples of verb forms

Basic PL3 Present SG1 -ko PL2 imperative Explanation
nukkua he nukkuvat nukutko? Nukkukaa! word containing the vowels AOU gets -a
kantaa he kantavat kannatko? Kantakaa! word containing the vowels AOU, gets -a
seisoa he seisovat seisotko? Seisokaa! word containing the vowels AOU, gets -a
syödä he syövät syötkö? Syökää! word without the vowels AOU, gets -ä
pelätä he pelkäävät pelkäätkö Pelätkää! word without the vowels AOU, gets -ä
sienestää he sienestävät sienestätkö Sienestäkää! word without the vowels AOU, gets -ä

Vowel harmony is important during:

  • Derivation is when a word has been formed with another word as its base or root, e.g. words ending in -uus/-yys and -ton/-tön.
  • Nouns are inflected when you add a grammatical case to them, e.g. when you add -ssa/-ssä or -lla/-llä to them.
  • Verbs are conjugated when you put them in e.g. the third person present (-vat/-vät) or the plural imperative (-kaa/-kää).
  • Suffixes will also do the same thing, e.g. -han/hän and -ko/-kö.
  • tuhma : tuhm-uus : tuhma-ssa : tuhma-ko
  • tyhmä : tyhm-yys : tyhmä-ssä : tyhmä-kö
  • valittaa : valit-us : valitta-vat : valitta-kaa : valitat-ko
  • välittää : välit-ys : välittä-vät : välitt-kää : välität-kö

When adding these endings to words that solely have the vowels E and I, you will use –yys, -ssä, -kö, etc.

  • kieli : kiel-tä : kiele-tön : kiele-ssä : kieli-kö
  • kiltti : kiltti-ä : kiltt-eys : kilti-llä : kiltti-hän

3. Compound Words

Compound words aka yhdyssanat can have a mix of both vowel groups, when you combine two words from different vowel groups.

  • sivu+pöytä aka side table
  • ilta+päivä aka “evening day” means afternoon
  • jää+kaappi aka “ice cupboard” means fridge
  • t+maa aka “work ground” means building site
  • syys+kuu aka “autumn moon” means September

When you inflect these words, the suffix you add will follow the vowel harmony rule for the last part of the word:

  • sivu+pöydä+llä
  • ilta+päivä+nä
  • jää+kaapi+sta
  • t+maa+ta
  • syys+kuu+ssa
  • maa+tie+llä
  • pesu+sieni+ä
  • kieli+kuva+na

4. Exceptions

There’s a fairly large amount of vowel harmony exceptions to this rule, most of which are the result of loanwords that have been adopted into the Finnish language. Not all these words have been adjusted to follow the Finnish vowel harmony rules, so they create irregularities.

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Andrea O'Brien

If I may make a comment about the site in general: I’ve been seriously studying Finnish for six weeks (after two years of haphazard and irregular struggle). This website makes the grammar rules clear, when nothing else is helpful! Deeply grateful!


hi, why the word muki end with i, but it becomes mukissa

Inge (admin)

You have to look at the whole word: there’s an -u- in the word as well, so it’s -ssa, not -ssä.


Thank you so much. Can you explain me when will we look at the final vowel and when will we look at the first vowel? And in case a word have 3 syllables, so which syllable we have to look at?

Inge (admin)

All of them! You need to look at all of them all the time, be the word short or long!

The only exception is compound words, which is explained in section #3.


Hi, I’m trying to learn Finnish right now and I want to know why the statement “in Binmaley”, is translated to Binmaleyssä and not Binmaleyssa? Why the need to use -ssä rather than -ssa?

Last edited 1 year ago by ALFIE P.
Inge (admin)

I suppose it could be both. Binmaley is such an unknown place that it’s hard to say.

Foreign placenames sometimes get -ssa vs. -ssä based on how the placename is pronounced. If you’re saying something that sounds more like “Binmäley” or “Binmeley”, that could explain the -ssä ending you’ve come across. However, -ssa would make more sense because Finns are very unlikely to know how this name is pronounced.


May I know “Tänään” is should be “Tanaan” ? Because it’s not containing vowels AOU in this word? Could you please explain that? Thanks in advance!

Inge (admin)

Tänään is a basic word. Words in their basic form can have all the vowels. For example, saari mean “island” and sääri means “shin”. Those are the basic forms of both the words.