Irregular and Umlaut Plurals | Norwegian Grammar

Most Norwegian nouns make their plural by adding -er and -ene, which the regular-plurals page covers. But a small, closed set of extremely common nouns does something else: they change their stem vowel in the plural — mann becomes menn, bok becomes bøker, fot becomes føtter. Linguists call this umlaut (or omlyd in Norwegian), and the good news for English speakers is that you already own the pattern. English kept exactly the same vowel-shifting plurals in man/men, foot/feet, tooth/teeth, goose/geese. You are not learning a strange new mechanism — you are just learning which Norwegian words use the one you grew up with, and which vowel pairs they shift between.

You already know this pattern

Before the rules, the reassurance. English and Norwegian inherited these umlaut plurals from the same Germanic ancestor, so the irregulars line up almost one-to-one:

English	Norwegian
man → men	mann → menn
foot → feet	fot → føtter
tooth → teeth	tann → tenner
book → books (regular in Eng.)	bok → bøker (umlaut in Nor.)

The mechanism is identical; only the specific vowels differ. So your job is not "memorise an irregular system" but "map the English irregular you already feel onto its Norwegian vowel". That is a far smaller task — and it is the memory hook most textbooks skip.

💡

These are the highest-frequency nouns in the language (man, woman, book, foot, night, hand, mother, father). Because you meet them constantly, the small upfront effort of memorising the four forms pays back faster than for any other vocabulary.

The full four forms — learn them as a set

As with all Norwegian nouns, you should learn each irregular as its full four-form grid, because the definite plural is where learners stumble. Here are the core umlaut nouns:

Singular	Definite sg.	Plural	Definite pl.	Gloss
en mann	mannen	menn	mennene	man
ei/en bok	boka/boken	bøker	bøkene	book
en fot	foten	føtter	føttene	foot
ei/en natt	natta/natten	netter	nettene	night
ei/en hånd / hand	hånda/hånden	hender	hendene	hand
en bonde	bonden	bønder	bøndene	farmer
ei/en and	anda/anden	ender	endene	duck
en tann	tannen / tanna	tenner	tennene	tooth
et tre	treet	trær	trærne	tree

Notice that the definite plural is built on the umlauted stem, not the singular: menn → mennene, bøker → bøkene, føtter → føttene. You take the plural form and add the definite ending; you do not go back to the singular vowel. This is the single most common slip.

To menn sto og ventet utenfor porten.

Two men stood waiting outside the gate.

Bøkene står i alfabetisk rekkefølge i hylla.

The books are in alphabetical order on the shelf.

Føttene mine er iskalde etter turen.

My feet are freezing after the walk.

The vowel shifts to watch

The umlaut nouns cluster around a few recurring vowel changes. Knowing the pattern won't let you predict which nouns umlaut, but it will help you remember the right vowel once you know a noun is in the club:

Shift	Examples
a → e	mann → menn, hånd → hender, tann → tenner, natt → netter, and → ender
o → ø	bok → bøker, fot → føtter, bonde → bønder, rot → røtter (root)
o → ø (kin)	mor → mødre, bror → brødre (see family-nouns)
special	tre → trær (tree), far → fedre (father)

Vi plantet tre nye trær i hagen i fjor.

We planted three new trees in the garden last year.

Bøndene i dalen dyrker mest poteter og korn.

The farmers in the valley grow mostly potatoes and grain.

Jeg har ikke sovet skikkelig på flere netter.

I haven't slept properly for several nights.

There is no deeper logic telling you that bok umlauts but kok (en kokk → kokker, "cook") does not — these are historical survivals, and the set is closed (no new noun joins it). That is the honest situation: you simply memorise the membership list. The list, however, is short and made of words you use every day, so it sticks fast.

💡

Build each irregular from its plural stem, not its singular. The definite plural of bok is bøkene (from bøker), never "bokene"; the definite plural of mann is mennene (from menn), never "mannene".

The kinship irregulars

Several of the most important irregulars are family words, and they shift vowels too — far → fedre, mor → mødre, bror → brødre, datter → døtre. Because kinship terms have their own quirks (reduced colloquial forms, the mormor/farmor system), they get a dedicated page; just note here that they belong to this same umlaut family.

Begge brødrene mine bor i utlandet nå.

Both my brothers live abroad now.

Mødrene satt og pratet mens barna lekte.

The mothers sat chatting while the children played.

Common Mistakes

Regularising the umlaut nouns. The biggest error: treating an irregular as if it took plain -er, keeping the singular vowel.

❌ Det var mange manner i salen.

Incorrect — 'man' umlauts: the plural is menn.

✅ Det var mange menn i salen.

There were many men in the hall.

Keeping the singular vowel for "book". Bok shifts o → ø in the plural.

❌ Jeg kjøpte tre boker.

Incorrect — the plural of bok is bøker (o → ø).

✅ Jeg kjøpte tre bøker.

I bought three books.

Building the definite plural from the singular. The definite plural sits on the umlauted stem.

❌ Mannerne / mannene gikk hjem.

Incorrect — it's mennene, built on the plural menn.

✅ Mennene gikk hjem.

The men went home.

Wrong vowel in -er-class kin and night words. Natt and hånd shift a → e, not anything else.

❌ Jeg har vært våken i tre natter… (vowel kept as a)

Incorrect spelling of the stem — the plural is netter (a → e).

✅ Jeg har vært våken i tre netter.

I've been awake for three nights.

Treating tre ('tree') as a zero-plural neuter. It looks like a one-syllable neuter, but it umlauts: tre → trær.

❌ Vi felte fem tre i skogen.

Incorrect — the plural is trær, not 'tre'.

✅ Vi felte fem trær i skogen.

We felled five trees in the forest.

Key Takeaways

A closed, high-frequency set of nouns forms the plural by changing the stem vowel (umlaut), not by adding plain -er: mann → menn, bok → bøker, fot → føtter, natt → netter, bonde → bønder, tre → trær.
The main shifts are a → e (mann/menn, tann/tenner, natt/netter) and o → ø (bok/bøker, fot/føtter, bonde/bønder).
Build the definite plural on the umlauted stem: bøkene, mennene, føttene — never from the singular vowel.
English already has this pattern (man/men, foot/feet), so you are mapping a familiar mechanism onto Norwegian vowels — but the membership list itself must be memorised.

Now practice Norwegian

Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.

Start learning Norwegian→