A diphthong is a vowel that moves — the tongue glides from one position to another inside a single syllable, the way English house slides from "ah" to "oo". Dutch has exactly three core diphthong sounds, but they're spelled with five different digraphs, because two pairs sound identical: ui (huis), ij/ei (mijn, klein), and au/ou (koud, vrouw). Learning them is two jobs at once — hearing three sounds, and remembering that ij and ei are the same sound, as are au and ou. This page is about the sounds; which digraph to write (ij vs ei, au vs ou) is a separate, notorious problem covered in ij/ei and au/ou spelling. The long pure vowels (aa, ie, oo…) that don't glide are in long and short vowels.
UI — the one with no English anchor at all
ui (huis, tuin, ui) is the hardest sound in Dutch for English speakers, because there is no English vowel even close to it. It's a diphthong that starts somewhere around the vowel of English house (or the short Dutch u of bus) and glides toward a front rounded position — toward the uu of muur, with the lips rounding as the tongue moves forward. The result is a gliding sound that English ears often can't place at all.
The best way in is to build it from parts you already have: start from the "uh" of bus, and glide toward the front-rounded uu (see front rounded vowels for that target). The lips round and the tongue moves forward together. Do not glide toward "ee" (that gives English oy) and do not glide toward "oo" (that gives English ow).
huis
'house' — start near 'uh', glide to a front-rounded uu. No English equivalent; do not say 'hows' or 'hoys'.
ui
'onion' — the diphthong on its own; a gliding sound that rounds toward the front.
tuin
'garden' — ui before n; keep the glide moving forward and rounded.
IJ / EI — close to English "ay"/"eye", but not identical
ij and ei are the same sound — they are homophones. mij and wei, rijst and eis, share one vowel. The sound is a diphthong starting around the "e" of bed and gliding up toward "ee" — close to English eye in some Dutch speakers and closer to English ay (as in day) in others, but in standard Dutch it sits between the two and is a touch more open and front than either English diphthong. Aim for a short, crisp glide from "eh" toward "ee"; don't stretch it into a long drawn-out English "aaay".
Because ij and ei sound identical, native children — and adults — make spelling mistakes here constantly. There's no audible clue to which one a word uses; you have to know it word by word (handled in ij/ei and au/ou spelling).
mij
'me' — ij; a crisp glide from 'eh' toward 'ee'. Sounds the same as any ei word.
wij
'we' — same ij vowel as mij; not English 'why', a tighter, more front glide.
klein
'small' — ei here, but identical in sound to an ij word like klijn would be.
trein
'train' — ei; note it's the same diphthong as in mij/wij despite the different spelling.
AU / OU — close to English "ow" of cow
au and ou are also the same sound, and this one English speakers nearly own already: it's very close to the ow of English cow / house — a glide from "ah" toward "oo". koud and gauw, vrouw and blauw all share this vowel. The Dutch version is a little tighter and the second element a little more rounded than a broad American "ow", but if you say the vowel of now, you'll be understood immediately.
As with ij/ei, the au/ou split is purely a spelling problem — there's no sound difference, so blauw and vrouw rhyme perfectly despite the different digraphs.
koud
'cold' — ou, the 'ow' of 'cow'; 'kowt' (final d devoices to t).
vrouw
'woman' — ou + w; rhymes with English 'now'.
blauw
'blue' — au, the same 'ow' sound as ou; blauw and vrouw rhyme.
gauw
'soon/quickly' — au; a tight 'ow' glide.
Three sounds, five spellings — the homophone map
| Sound | Spellings | English anchor | Examples |
|---|---|---|---|
| ui | ui | none — build it from 'uh' → front-rounded uu | huis, tuin, ui |
| ij/ei | ij and ei (homophones) | between English 'ay' and 'eye' | mij, wij, klein, trein |
| au/ou | au and ou (homophones) | 'ow' of 'cow' | koud, vrouw, blauw, gauw |
The IJ quirk: a digraph that behaves like a letter
Here's the detail competitors skip. Among all Dutch digraphs, ij is unique: it isn't just a spelling of a sound, it behaves like a single letter — the so-called lange ij ("long ij"). Three consequences:
- It capitalises as a unit. When a word starting with ij is capitalised, both letters go uppercase: the country IJsland ("Iceland"), the town IJmuiden, the river IJssel. You never write "Ijsland". No other Dutch digraph does this.
- It fills one slot in puzzles and old dictionaries and can be alphabetised with y in some traditional orderings.
- In handwriting and signage it's often drawn as a single glyph resembling ÿ.
This is purely orthographic — the sound is the same ij/ei diphthong — but it's a quirk worth flagging now and is detailed in capitalisation and IJ.
IJsland
'Iceland' — both letters of the ij capitalise. Never 'Ijsland'.
Het is koud in IJmuiden.
'It's cold in IJmuiden.' — the place name keeps the double-capital IJ mid-sentence too.
Common Mistakes
❌ huis pronounced as English 'hows' or 'house'
Wrong — that's the au/ou sound; ui glides toward a FRONT-rounded vowel, not back toward 'oo'.
✅ huis (glide from 'uh' to front-rounded uu)
'house'.
❌ huis pronounced as 'hoys' / tuin as 'toyn'
Wrong — gliding toward 'ee' gives English 'oy'; ui rounds the lips and moves forward.
✅ tuin (rounded forward glide)
'garden'.
❌ Reading the ij in mijn as the English letter sound, 'mine' → 'em-eye-jay-en'
Wrong — ij is one diphthong vowel, not the spoken letters; mijn ≈ 'mein'.
✅ mijn (one ij diphthong)
'my/mine'.
❌ Assuming ij and ei (or au and ou) sound different
Wrong — each pair is homophonous; the difference is purely how you spell it.
✅ klein = klijn would be; blauw rhymes with vrouw
'small'; 'blue' rhymes with 'woman'.
❌ Writing the country as 'Ijsland'
Wrong — the ij digraph capitalises as a unit: IJsland.
✅ IJsland
'Iceland'.
Key Takeaways
- Dutch has three diphthong sounds in five spellings: ui, ij/ei, au/ou.
- ui has no English equivalent — build it from the u of bus gliding into the front-rounded uu of muur. Not "ow", not "oy".
- ij and ei are homophones (a crisp "eh"→"ee" glide, between English ay and eye); au and ou are homophones (the "ow" of cow).
- Because the pairs sound identical, which digraph to write is a memorised, per-word fact — see ij/ei and au/ou spelling.
- ij is a quasi-letter: it capitalises as a unit — IJsland, IJmuiden — a quirk no other digraph shares.
Now practice Dutch
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Start learning Dutch→Related Topics
- Long and Short VowelsA1 — Dutch a/aa, e/ee, i/ie, o/oo, u/uu pairs differ in tongue position, not just length — and this short/long contrast is the engine behind Dutch consonant doubling in spelling.
- Front Rounded Vowels: UU and EUA2 — Dutch uu (nu, vuur) and eu (deur, neus) are front rounded vowels with no English counterpart — produced by saying a front vowel and then rounding the lips, and easily confused with the diphthong ui and the back vowel oe.
- OE and Other Vowel DigraphsA2 — Dutch oe is the English 'oo' of 'food' — the one vowel digraph English speakers already own — plus the glide sequences aai/ooi/oei/eeuw/ieuw and the reduced endings -ig and -lijk that don't sound the way they look.
- Writing IJ vs EI and AU vs OUB1 — Dutch's two great homophone spelling problems: ij (lange ij) and ei (korte ei) sound identical, as do au and ou, so the choice is lexical, not phonetic — there is no pronunciation rule, only a handful of reliable morphemes and high-frequency words to memorise.
- Capitalization and the Capital IJA2 — Dutch capitalises far less than English — days, months and the pronoun ik all stay lowercase — but adjectives from country and place names keep their capital (Franse kaas), and when a word beginning with ij is capitalised, both letters go up: IJsland, never Ijsland.