Irregular Dutch plurals: steden, kinderen, musea

Most Dutch nouns build their plural with -en or -s. A small group does neither: de stad (the city) becomes de steden (the cities), not stadden, and het kind (the child) becomes de kinderen (the children). These plurals are worth learning one by one.

There is no single rule; these plurals fall into three small groups you learn by heart. Once you know which group a word belongs to, the form is fixed.

1. A changed vowel in the last syllable: stad → steden, schip → schepen.
2. The ending -eren instead of -en: kind → kinderen, ei → eieren.
3. The Latin endings -a and -i on borrowed words: museum → musea, musicus → musici.

In this group the vowel of the last syllable changes when you add -en. Often a short vowel turns long because the extra syllable opens it up (more on this in open and closed syllables); in a few words the vowel letter itself changes.

Note that schip and lid swap the i for an e, and stad swaps a for e. The same i → e swap appears in de smid (the smith) → de smeden. A regular short-vowel plural would double the final consonant (as in man → mannen), but because the vowel here becomes long, the consonant stays single: stad keeps one d in steden, not stadden.

About fifteen nouns build their plural with -eren rather than plain -en. This is a closed set: you cannot add new words to it and there is no clue in the singular, so treat it as a short vocabulary list to memorise. Every member is a het-word on its own, and — like any Dutch plural — it switches to de once plural: het kind → de kinderen.

The two spelling notes come from rules you already know. Lam has a short a, so the m doubles before the ending to keep that vowel closed — de lammeren, the same doubling as in man → mannen. And the f of kalf softens to a v once it sits between vowels; this is the shift covered under v becomes f, z becomes s, and you meet it in ordinary plurals too, as when de brief (the letter) becomes de brieven.

Words borrowed from Latin can keep their Latin plural. Nouns ending in -um replace it with -a, and nouns for people ending in -us replace it with -i. Many of these also have an everyday Dutch plural in -s, which is equally correct.

For the -um words the -a form is the more common one in writing (musea, centra). The -us → -i words for people normally have only the Latin plural: you say de musici, not de musicussen.

A couple of nouns keep both an -en and an -eren plural, and the two are not interchangeable: each ending locks onto a different meaning, so you choose by sense.

• het been: the everyday plural is de benen (the legs); the -eren form de beenderen — with a d slipped in before the ending — means bones, the kind in a skeleton.
• het blad: de bladen are flat sheets (pages, trays, a magazine's issues), while de bladeren are the leaves growing on a tree.

A lookalike case is worth separating out. Sometimes two entirely different nouns share one spelling. Het pad (the path) has the regular plural de paden, but de pad (the toad) is a different word altogether and makes de padden. Here the article, not a shift in one noun's meaning, tells you which plural belongs.

The trap is treating these nouns as regular. There is no way to hear or see from the singular that stad takes steden or that kind takes kinderen — stadden and kinden are simply wrong. Because the form is unpredictable, learn each of these nouns together with its plural, the same way you learn a noun with its de or het article.