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Dutch diphthongs

A diphthong is one vowel that glides into another inside a single syllable. Dutch has three “true” diphthongs — ij/ei, ui and ou/au — plus a set of rarer semi-diphthongs formed when a long vowel glides into a w or j off-glide. Here they all are, with mouth positions and practice words.

The big three

These three account for almost all Dutch diphthongs in running text. Two of them have no English equivalent, which is why they get their own dedicated pages.

ij / ei [ɛi]

One sound, two spellings. Start at the vowel of English bed and glide up towards “ee”, lips unrounded. ijs (ice), trein (train), klein (small). Which spelling a word takes is memorised, not heard — the full story, including the schwa-pronounced -lijk ending and the capital IJ, is on the ij and ei page.

ui [œy]

The hardest vowel in Dutch and the one with no English counterpart. Round and push your lips forward, front your tongue to the “eh” area, then glide up towards “y” keeping the lips pursed throughout. huis (house), tuin (garden), uit (out). Do not let it collapse into English “ow”. Step-by-step drills are on the ui sound page.

ou / au [ɑu]

The one true diphthong English speakers already own: it is essentially the “ow” of house. Start at open “ah” and glide to “oo”. koud (cold), vrouw (woman), blauw (blue), saus (sauce). Like ij/ei, the two spellings ou and au sound identical; which one to write is fixed per word. The one caution: keep it distinct from ui — koud and a would-be *kuid must not merge.

The semi-diphthongs: long vowel + glide

Dutch forms a second family of diphthong-like sounds by adding a w-glide [u] or j-glide [i] to a long vowel. These are less frequent but appear in common words, and English speakers tend to under-pronounce the glide. Say the long vowel fully, then add a distinct off-glide.

The one that catches English speakers most is ieuw in nieuw (new): it is “nee” + a clear w, roughly “NEE-oow”, not “new”. Likewise leeuw is “LAY-oow” and mooi is “MOH-y” with a firm y at the end.

Contrast drill: keep the three big ones apart

The classic learner failure is merging ui, ou/au and even ij/ei into one English-flavoured glide. Drill them in a set:

North and south

The diphthongs are a well-known regional tell. In the Netherlands' Randstad the big three are often pronounced with wide, lowered starting points — the so-called “Poldernederlands” tendency, where ij drifts towards [ai] and ui and ou open up noticeably. In Flanders (Belgium) and the southern Netherlands the same diphthongs are tighter, higher and sometimes barely glide at all, so ij/ei can sound almost like a long monophthong [ɛː]. Both patterns are standard; a learner is safe copying either, as long as the three stay distinct from one another. This is part of the broader Dutch vs Flemish difference.

Full practice list

The two hardest diphthongs earn deeper treatment: the ui sound and ij vs ei. For the non-gliding vowels and the long–short system behind them, see Dutch vowels.