Have you ever noticed that Finnish sounds very melodic?

There’s actually a grammatical reason for this. It’s called Vowel Harmony (or vokaaliharmonia in Finnish).

When I first introduce this concept to my students, they often get worried because it sounds like a complex musical theory.

Don’t worry. It’s actually quite logical.

Once you understand the basic rules, you’ll instinctively know which endings to add to words without even thinking about it. It helps your pronunciation flow and makes your spelling accurate.

In this guide, I’ll break down the three vowel groups and how to use them.

The 3 groups of Finnish vowels

In English, you can mix any vowels you want in a single word.

In Finnish, words are picky. They don’t like mixing certain vowels together.

To understand this, we need to look at the vowels. There are 8 vowels in the Finnish alphabet, and we divide them into three specific teams.

The teams are determined by where your tongue is positioned in your mouth when you say them.

Here is the big secret:

• Back Vowels (A, O, U) are the strong, dominant vowels.
• Front Vowels (Ä, Ö, Y) are the lighter vowels (usually with dots).
• Neutral Vowels (E, I) are the friendly ones that can hang out with anyone.

The golden rules of harmony

Finnish is an “agglutinative” language. This means we glue endings (suffixes) onto words to change their meaning.

For example, to say “in the house,” we add -ssa to talo (house).

Because of vowel harmony, most Finnish endings come in two versions: one with back vowels (A, O, U) and one with front vowels (Ä, Ö, Y).

• -ssa / -ssä (in)
• -sta / -stä (from)
• -ko / -kö (question particle)

You have to pick the right one to make the word sound harmonious.

Rule 1: Back vowels stay together

If a word contains A, O, or U, the whole word is considered a “Back Vowel” word. You must use the ending that has A, O, or U.

Even if there’s an i or e in the word, the presence of A, O, or U overpowers them.

(Note: ‘Kissa’ has an ‘A’, so we use the ending ‘a’ in ‘Missä’, right? Actually, ‘Missä’ is a front vowel word, but look at ‘Kissa’. If we added an ending to Kissa, it would be heavy.)

Let’s look at a clearer example with the suffix -ssa (in).

Talo (House) has A and O. It’s a back vowel word. Correct: Talossa Incorrect: Talossä

Rule 2: Front vowels stay together

If a word has Ä, Ö, or Y (and does not have A, O, or U), it’s a Front Vowel word. You must use the endings with dots (Ä, Ö) or Y.

Metsä (Forest) has E and Ä. Because of the Ä, it’s a front vowel word.

• Correct: Metsässä
• Incorrect: Metsässa

Työ (Work) has Y and Ö.

• Correct: Työssä
• Incorrect: Työssa

How to handle neutral vowels (E and I)

This is the part that confuses beginners the most, but it’s actually very simple.

The vowels E and I are neutral. They are like chameleons.

1. When mixed with others

If a word has E or I mixed with Back Vowels (A, O, U), the word is Back.

• Tuoli (Chair) -> Tuolissa (In the chair).

If a word has E or I mixed with Front Vowels (Ä, Ö, Y), the word is Front.

• Leipä (Bread) -> Leipää (Some bread).

2. When they are alone

If a word contains only neutral vowels (E and I) and no others, it usually behaves like a Front Vowel word.

This means you use the endings with dots (Ä, Ö, Y).

Tie (Road)

This word only has I and E.

• Correct: Tiellä (On the road)
• Incorrect: Tiella

Helsinki

This word only contains E and I.

• Correct: Helsingissä (In Helsinki)
• Incorrect: Helsingissa

Compound words and exceptions

Finnish loves compound words (putting two words together to make a new one).

For example: Jääkaappi (Fridge).

• Jää (Ice) = Front vowel
• Kaappi (Cupboard) = Back vowel

So, which harmony rule do we use?

The Rule: In compound words, vowel harmony is determined by the last part of the word.

Since kaappi is the last part of jääkaappi, and kaappi is a back vowel word (A), the ending must be back.

(Not Jääkaapissä)

A note on colloquial Finnish (Puhekieli)

In standard written Finnish (Kirjakieli), these rules are very strict.

However, in spoken Finnish or some regional dialects, you might hear slight variations, especially with loan words (words borrowed from other languages).

For example, the word Olympialaiset (Olympics).

Strictly speaking, it has back vowels (O, A). But because it’s a loan word, some Finns might pronounce it closer to the front of the mouth.

However, as a learner, you should stick to the standard rules I listed above. They work 99% of the time!

Summary

If you ever get stuck deciding between -a or -ä, just look at the word you’re attaching it to.

1. Does it have A, O, U? -> Use A, O, U endings.
2. Does it have Ä, Ö, Y? -> Use Ä, Ö, Y endings.
3. Does it have only E, I? -> Use Ä, Ö, Y endings.