Writing IJ vs EI and AU vs OU | Dutch Grammar

Almost all of Dutch spelling is predictable from sound — but here are the two places where it genuinely is not. The digraph ij (called lange ij, "long ij") and the digraph ei (korte ei, "short ei") are pronounced exactly the same. So are au and ou. When you hear one of these sounds, your ear cannot tell you which spelling to write, because both spellings sound identical. The choice is lexical — a property of the individual word that you must know — not phonetic. This page is honest about that: there is no clever rule that resolves it, so instead of inventing one, we give you the reliable morphemes plus a curated, frequency-ordered list of the words worth memorising. (For how the sounds themselves are produced, see the diphthongs; this page is purely about which letters to write.)

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Dutch children spend years drilling ij/ei and au/ou in school, and adults still look words up. If even native speakers memorise these word by word, so will you — and that's not a gap in your knowledge, it's the actual nature of the problem.

Why there is no rule

ij and ei both spell the same diphthong (roughly "ay" gliding toward "ee", as in mij, klein). Centuries ago they may have differed in sound, but in modern standard Dutch they merged completely. The spellings stayed frozen the way the words happened to be written, so today the distinction carries no pronunciation information at all — it survives only as a historical fingerprint on each word. The same is true of au and ou: identical sound (a diphthong like "ow" in English now), two frozen spellings.

So when a teacher or app tells you there's a "trick" to hearing the difference, be sceptical: in the standard language there is nothing to hear. What does help is (1) a small set of morphemes that are 100% reliable, and (2) knowing the highest-frequency words by heart.

The reliable morphemes for ij

A few endings and grammatical pieces always use ij. These are worth their weight in gold because they cover a large share of the ij you'll ever write:

-lijk / -lijke — the adjective/adverb ending: mogelijk, eindelijk, vrolijk, natuurlijk, gemakkelijk, dadelijk. Always ij. (It's pronounced as a weak -luk, but it's spelled -lijk.)
-tijd in time words: tijd, altijd, tijdens, intijds, tegelijkertijd.
The pronouns and very common grammar words: mij, wij, zij, jij, hij, zijn, mijn, wijzelf.
The -erij / -arij noun ending (a place or activity): bakkerij, slagerij, brouwerij, woestenij.

Het is eindelijk mogelijk om dat gemakkelijk te regelen.

'It's finally possible to arrange that easily.' Three -lijk words, all ij — guaranteed by the ending.

Wij zien hem altijd op zijn fiets.

'We always see him on his bike.' wij, altijd, zijn — all ij, all high-frequency function words.

The high-frequency ij words to memorise

Beyond the morphemes, learn these core words with ij. They are everywhere:

ij word	Meaning	ij word	Meaning
mij, wij, zij, jij, hij	me, we, they/she, you, he	zijn, mijn	his/to be, my
fiets	bike	blijven	to stay
krijgen	to get	schrijven	to write
kijken	to look	rijden	to drive/ride
tijd, altijd	time, always	vrij, vrijdag	free, Friday
wijn	wine	prijs	price
lijken, gelijk	to seem, equal/right	vijf	five

Ik krijg vrijdag mijn nieuwe fiets.

'I get my new bike on Friday.' krijg, vrijdag, mijn — all lange ij.

The high-frequency ei words to memorise

Now the ei side. Fewer high-frequency words, which is why drilling the short list pays off:

ei word	Meaning	ei word	Meaning
klein	small	trein	train
eind, einde	end	geit	goat
ei	egg	reis, reizen	trip, to travel
leiden, leider	to lead, leader	weide	meadow
reiken	to reach	zeil	sail
eisen	to demand	meisje	girl
keizer	emperor	heilig	holy
het feit	the fact	geheim	secret

Het meisje neemt de trein naar het einde van de lijn.

'The girl takes the train to the end of the line.' meisje, trein, einde — all korte ei; lijn is ij.

Ik reis graag, maar dit was een klein avontuur.

'I love to travel, but this was a small adventure.' reis, klein — ei.

Two memory hooks that actually help

There is no phonetic rule, but two associative tricks reduce the load:

The -lijk anchor. Whenever the syllable means "-ly / -able / -ish" or ends an adjective (mogelijk, vriendelijk), it's ij, no exceptions. This single anchor handles a huge slice of cases.
The "ei twins" rhyme. A traditional Dutch mnemonic lists the ei words together so the short list sticks: ei, reis, trein, klein, eind, meisje, geit — say them as a set. Everything not in your memorised ei set defaults to ij (since ij is the more common spelling overall).

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Strategy: memorise the shorter ei list and the -lijk ending, then default to ij. Because ij is the statistically more common spelling, "if it's not on my ei list, write ij" is a surprisingly good betting rule — though never a guarantee.

AU vs OU: the same problem, smaller scale

au and ou are identical in sound, and again the choice is lexical. The lists are short enough to learn outright.

Common au words: gauw (soon), blauw (blue), nauw (narrow), paus (pope), saus (sauce), flauw (faint/bland), rauw (raw), augustus (August), automobiel/auto (the loanword au).

Common ou words: koud (cold), oud (old), goud (gold), vrouw (woman), vouwen (to fold), hout (wood), zout (salt), bout (bolt), mout (malt), schouder (shoulder), houden (to hold/keep), trouwen (to marry).

In de koude winter draagt de oude vrouw een blauwe sjaal.

'In the cold winter the old woman wears a blue scarf.' koud, oud, vrouw → ou; blauw → au.

Doe gauw wat zout in de saus.

'Quickly put some salt in the sauce.' gauw, saus → au; zout → ou.

One weak helper: the cluster -oud / -out / -ouw is very often ou (koud, oud, goud, hout, zout, vrouw, trouwen, schouder, houden), so when you hear that ending shape, betting on ou wins more often than not. But gauw, blauw, nauw, flauw, rauw break it (they're au before -w), so it's a tendency, not a law.

A note on the capital: IJ

When ij starts a word and you capitalise it, both letters capitalise together: IJsselmeer, IJsland (Iceland), IJmuiden, the name IJsbrand. Writing Ijsland with a lowercase j is a real and common error. This is because ij behaves as a single letter in Dutch. Full treatment on capitalisation and IJ.

We zeilen op het IJsselmeer en daarna naar IJsland.

'We sail on the IJsselmeer and then to Iceland.' Capital IJ on both — never Ijsselmeer.

Common Mistakes

❌ eindelijk spelled 'eindeleik'

Wrong — the -lijk ending is always ij: eindelijk.

✅ eindelijk

'finally' — -lijk is a guaranteed ij.

❌ trein spelled 'trijn'

Wrong — trein is one of the core ei words.

✅ trein

'train' — korte ei.

❌ wijn ('wine') spelled 'wein'

Wrong — wijn is lange ij; wein doesn't exist.

✅ wijn

'wine' — ij.

❌ koud spelled 'kaud'

Wrong — the -oud cluster takes ou: koud.

✅ koud

'cold' — ou.

❌ Ijsland with a lowercase j

Wrong — initial ij capitalises as a unit: IJsland.

✅ IJsland

'Iceland' — capital IJ.

Key Takeaways

ij/ei and au/ou sound identical — the choice is lexical, not phonetic. There is no honest pronunciation rule.
The -lijk ending is always ij; pronouns and common grammar words (mij, wij, zijn, tijd, altijd) are ij.
Memorise the shorter ei list (klein, trein, eind, meisje, geit, reis, ei...) and default to ij for the rest.
au/ou is the same problem on a smaller scale — learn the two short lists; -oud/-out/-ouw tends toward ou, but gauw/blauw/nauw break it.
Initial IJ capitalises as a unit: IJsselmeer, IJsland — never Ijsland.

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