Irregular and Special Plurals | Dutch Grammar

Most Dutch plurals are predictable: add -en (and re-spell the stem) or add -s. This page collects the nouns that break those rules — the ones you have to learn as facts rather than derive. There are four kinds: a set of words that lengthen their vowel in the plural (stad → steden), a tiny but high-frequency class taking -eren (kind → kinderen), the Latin and Greek loans that keep a foreign plural (museum → musea), and the everyday -en plurals that need a trema because the -en lands on a vowel (idee → ideeën). None of these is huge, but every one is made of words you use constantly, so they're worth memorising directly.

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"Irregular" here doesn't mean "rare." These are some of the most common nouns in the language — child, egg, city, ship, day. Frequency is exactly why they kept their old, irregular forms: words used every day resist being tidied up.

Vowel-lengthening plurals: short vowel becomes long

A small group of nouns with a short vowel in the singular switches to a long vowel in the plural — and the spelling shows it. The clearest case is stad → steden: the a doesn't just stay short and double its consonant (which would give the non-word stadden); instead the vowel changes quality and length to a long e, and the d is single because the syllable is now open (ste-den).

stad → steden (ste-den)

'city' → 'cities' — the short a becomes a long e; note it is NOT 'stadden' or 'staden'.

schip → schepen (sche-pen)

'ship' → 'ships' — short i becomes long e; the p is single in the open syllable.

In de middeleeuwse steden lagen de schepen vol in de haven.

In the medieval cities the ships lay full in the harbour.

The other members keep the same vowel letter but lengthen it across the open syllable — this is the ordinary open/closed-syllable behaviour, but it surprises learners because the singular's short vowel sounds nothing like the plural's long one:

Singular	Plural	Vowel shift	Meaning
stad	steden	short a → long e	city → cities
schip	schepen	short i → long e	ship → ships
dag	dagen	short a → long aa	day → days
weg	wegen	short e → long ee	road → roads
lid	leden	short i → long e	member → members
glas	glazen	short a → long aa (+ s→z)	glass → glasses
gebod	geboden	short o → long oo	commandment → commandments

The reason this catches English speakers off guard is that the singular does not warn you. Look at dag: in the singular the a is short and clipped (rhymes with the vowel in English bug roughly), but dagen has a long, open aa-quality vowel. You cannot see this in the spelling of dag alone — you simply have to know that dag, weg, slag, gat, and a handful of others lengthen.

dag → dagen

'day' → 'days' — the a lengthens; you hear a long aa in 'dagen' that isn't there in 'dag'.

Alle leden van de club kregen een glas champagne.

All the members of the club got a glass of champagne.

De wegen waren glad na drie dagen vorst.

The roads were slippery after three days of frost.

Note glas → glazen stacks two changes at once: the vowel lengthens and the s surfaces as a z between vowels (the same s↔z rule as huis → huizen). Likewise graf → graven and dak → daken combine lengthening with their other regular changes.

The -eren plural: a Germanic relic

A very small class adds -eren rather than -en or -s. There are only a handful of these, but they include some of the first nouns you ever learn, so the irregularity is unavoidable:

Singular	Plural	Meaning
kind	kinderen	child → children
ei	eieren	egg → eggs
blad	bladeren / bladen	leaf → leaves (see note)
kalf	kalveren	calf → calves
volk	volkeren / volken	people/nation → peoples
lam	lammeren	lamb → lambs
rund	runderen	head of cattle → cattle
been	beenderen	bone → bones (in the skeletal sense)

kind → kinderen

'child' → 'children' — the -eren plural, exactly cognate with the English form.

ei → eieren

'egg' → 'eggs' — note the i appears twice: ei + eren = eieren.

De kinderen hebben vanmorgen zes eieren gegeten.

The children ate six eggs this morning.

Here is the insight that makes this class memorable rather than arbitrary. The -eren plural is the same ancient Germanic ending that survives in English child → children and ox → oxen. English has only two relics left (children, the irregular plural; and the -en of oxen, brethren); Dutch kept a slightly bigger handful, but it's the same morphological fossil. When you say kinderen, you are saying a plural built the very same way as English children — even the extra -r- matches (English child-r-en, Dutch kind-er-en). Seen that way, kinderen is the least foreign plural in Dutch for an English speaker.

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Three of these have a doublet: blad = bladeren (leaves on a tree/plant) vs bladen (sheets of paper, magazines, trays); volk = volkeren (distinct peoples/nations) vs volken (same, slightly more neutral). The form you pick carries the meaning — they are not free variants.

De bladeren vallen in de herfst van de bomen.

The leaves fall from the trees in autumn. (bladeren = foliage)

Op tafel lagen stapels losse bladen papier.

Stacks of loose sheets of paper lay on the table. (bladen = sheets)

Latin and Greek loan plurals

Words borrowed from Latin and Greek — especially academic and technical vocabulary — often keep (or optionally keep) their classical plural. Two patterns dominate:

-um → -a: museum → musea, centrum → centra, gymnasium → gymnasia, medium → media.
-is → -es: crisis → crises, thesis → theses, basis → bases (the -is ending shifts to -es, pronounced -es).

museum → musea

'museum' → 'museums' — the Latin -um → -a plural; museums also occurs (see below).

crisis → crises

'crisis' → 'crises' — -is becomes -es, pronounced 'cri-ses'.

De grote musea in Amsterdam trekken jaarlijks miljoenen bezoekers.

The big museums in Amsterdam draw millions of visitors a year.

The complication — and it's a real one — is that many of these now allow a Dutch -s or -en plural alongside the classical one, and the two aren't always interchangeable in register. Museums and musea both occur; musea is the more formal/traditional choice, museums the more colloquial. Media (Latin plural of medium) has even drifted into being treated as a singular mass noun (de media berichtte...), exactly as in English.

Singular	Classical plural	Dutch plural	Note
museum	musea	museums	both common; musea more formal
centrum	centra	centrums	centra dominant in writing
politicus	politici	—	only the -i plural is standard
catalogus	catalogi	catalogussen	both occur
museum / lyceum	musea / lycea	—	-a strongly preferred

De meeste politici beloven van alles voor de verkiezingen.

Most politicians promise all sorts of things before the elections. (politicus → politici, only standard form)

There's no clean shortcut here: you have to learn, word by word, whether a given loan keeps only its classical plural (politici, never politicussen in standard Dutch), allows both (musea / museums), or has gone fully Dutch. When in doubt for a formal text, the classical plural is the safer choice; in speech, the Dutch -s is rarely wrong with the everyday ones.

The trema in -ën plurals

This last group isn't lexically irregular at all — it's the ordinary -en plural, but landing on a stem that already ends in a vowel letter. When -en is added to a word ending in -e (or another vowel that would clash), the resulting vowel sequence would be misread as a digraph. Dutch blocks that with a trema — the two dots — on the e of the ending. The trema is obligatory, not optional: leaving it out is a spelling error, not a stylistic choice.

idee → ideeën (i-dee-ën)

'idea' → 'ideas' — without the trema, 'ideeen' would read the ee+e as one long ee; the trema forces a fresh syllable.

knie → knieën (kni-e-ën)

'knee' → 'knees' — the trema splits the vowels into separate syllables.

zee → zeeën (zee-ën)

'sea' → 'seas' — zee + en, with the obligatory trema on the second e.

The members are exactly the nouns ending in a long vowel sound spelled with a final vowel letter: idee → ideeën, zee → zeeën, knie → knieën, industrie → industrieën, drie → drieën (used in met z'n drieën, "the three of us"). A second-syllable-stressed word like bacterie takes the trema directly on the final -e without an extra one (bacteriën, not bacterieën) — the stress-conditioned split is detailed on the trema page. The same trema appears whenever -en follows a vowel that could form a false digraph — so this overlaps with the spelling rule covered in full on the trema and apostrophe page.

We gingen met z'n drieën naar de zee en zagen wel honderd kwallen.

The three of us went to the sea and saw a good hundred jellyfish.

Hij zit vol ideeën, maar voert er nooit een uit.

He's full of ideas, but never carries a single one out.

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The test for the trema: does adding -en put an e directly after another vowel letter that could be read as a digraph? idee + en → ideeën; knie + en → knieën. If yes, the trema is mandatory. A word ending in a consonant (boek → boeken) never needs it.

Common Mistakes

The dominant English-speaker error is regularising these — assuming an -s (from English) or a plain -en where the Dutch form is irregular — plus dropping the obligatory trema.

❌ stads / stadden

Wrong — 'city' lengthens its vowel: the plural is steden, not an English-style -s or a doubled-consonant form.

✅ steden

'cities' — short a becomes long e.

❌ kinds / kinden

Wrong — 'child' takes the old -eren plural, just like English children.

✅ kinderen

'children'.

❌ eis / eien

Wrong — 'egg' is in the -eren class: eieren.

✅ eieren

'eggs'.

❌ ideeen / knieen (no trema)

Wrong — the trema is obligatory when -en lands on a clashing vowel: ideeën, knieën.

✅ ideeën, knieën

'ideas, knees'.

❌ politicussen

Wrong — this loan keeps only its Latin plural in standard Dutch: politici.

✅ politici

'politicians'.

Key Takeaways

A set of nouns lengthens its vowel in the plural: stad → steden, schip → schepen, dag → dagen, lid → leden, glas → glazen. The singular gives no warning — memorise them.
The small -eren class (kind → kinderen, ei → eieren, blad → bladeren, kalf → kalveren) is the same Germanic relic as English child → children and ox → oxen.
Latin/Greek loans often keep a classical plural: museum → musea, crisis → crises, politicus → politici. Many now allow a Dutch -s too (musea / museums), with the classical form the more formal choice.
The -ën plural is the regular -en with an obligatory trema when it lands on a vowel: idee → ideeën, zee → zeeën, knie → knieën, drie → drieën. Dropping the trema is a spelling error.

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