The -e Stems: kieli → kiele-

This is the class that catches almost every learner. A huge number of Finnish nouns end in -i in the dictionary, and you would reasonably expect them to keep that -i when you add endings. Many do not. Instead the -i is a disguise for an underlying -e- stem: kieli ("language") is really kiele-, so "of the language" is kielen, not *kielin. And the nominative gives you no clue which -i words do this and which keep their -i. Sorting out the split is one of the genuine hurdles of Finnish, and this page is built to make it navigable rather than mysterious.

The pattern: nominative -i, stem -e-

For an e-stem noun, the final -i of the dictionary form turns into -e- in the inflectional stem, and endings attach to that:

The genitive is the giveaway, exactly as the stem concept page promised: kielen minus -n leaves the stem kiele-. From there every ending is regular — kielessä (in the language), kielestä (from the language), kielelle (to the language).

The partitive: two sub-patterns

Watch the partitive of e-stems, because they split into two groups. Some take a plain vowel-stem partitive with -ä/-a; others reach for a consonant stem and take -tä/-ta:

The e-stems that end in -l, -n, -r, -s (like kieli, pieni, suuri, vesi) usually take the consonant-stem partitive -tä/-ta (kieltä, pientä, suurta, vettä); the rest take the vowel-stem -ä/-a (kiveä, ovea, nimeä). This overlap with the consonant stems is not a coincidence — those very words are the ones preserving an old consonant base.

The crucial contrast: loanwords that keep -i

Not every -i word is an e-stem. A large set — mostly newer loanwords — keeps the -i right through the paradigm as an ordinary vowel stem:

Here the stem is pankki-, bussi-, posti- — the -i never becomes -e-. So "of the bank" is pankin (with the -i still there, though kk gradates to k), not *panken.

How to tell them apart

Here is the honest part: the nominative alone does not tell you. Kieli (e-stem) and pankki (i-stem) look equally like -i words. There is no spelling rule that separates them with total reliability. But there is a strong historical tendency you can lean on:

• Old, native core vocabulary — body, nature, kinship, basic concepts — descends from an earlier -e and is almost always an *e-stem: kivi, vesi, veri, nimi, kieli, ovi, järvi, tuli, lumi, mäki, joki, suomi.
• Newer loanwords, especially those that end in a doubled consonant + i or simply "look foreign," are almost always i-stems: pankki, bussi, posti, kahvi, hotelli, paketti, netti, banaani.

Gradation hides inside the e-stem too

Because the stem is where gradation lives, moving -i to -e- can also flip a consonant. The clearest set is the -si subgroup, where an old t surfaces as d in the weak grade:

Vesi → veden shows t → d; joki → joen shows k → ∅ (the k disappears entirely). The -si words are so distinctive — with both this gradation and a consonant-stem partitive (vettä) — that they get their own -si words page.

How this differs from English

English has irregular plurals (foot → feet), but they are a closed handful you memorize as exceptions. In Finnish the -i/-e alternation is not an exception — it is a whole live class covering some of the commonest words in the language, and it runs through every case, not just the plural. An English speaker's instinct is to treat the written -i as fixed; the Finnish reality is that for native words that -i is a thin shell over an -e- underneath.

Common Mistakes

Key Takeaways

• A large class of -i nouns inflects on an -e- stem: kieli → kiele-, ovi → ove-, nimi → nime-.
• The genitive settles it: -en means e-stem, -in means the -i stays (loanwords like pankki, bussi).
• E-stem partitives split: vowel-stem -ä/-a (kiveä, nimeä) vs consonant-stem -tä/-ta (kieltä, suurta).
• Old native words tend to be e-stems; newer loanwords keep their -i.
• Gradation can hide in the stem too — the -si subgroup shows t → d (vesi → veden), covered on its own page.