Diphthongs: au, ei, ey, and the Accented Vowels | Icelandic Grammar

A diphthong is a single vowel that glides — it starts at one tongue position and slides to another within one syllable. Icelandic has several, and two of them are spelled with two-letter digraphs you have to recognise on sight: au and ei/ey. The accented letters á, ó, é, æ are also phonetically diphthongs, but because they involve the acute accent they get their full treatment on The Accented Vowels; here we point at them and concentrate on the digraphs. Of everything on this page, one sound deserves your fiercest attention: au. It is the most surprising vowel in the language for English speakers, and mispronouncing it is the classic foreign-accent tell.

au — the front-rounded glide that is NOT English "ow"

Read au and your English instinct screams "ow" (as in house) or your German instinct screams "ow" (as in Haus). Both are wrong. Icelandic au is starts at the front-rounded open vowel ö [œ] and glides up to a front-rounded high glide near y/i. The whole thing stays in the front of the mouth, with the lips rounded throughout. There is no English vowel even close to it — the nearest accidental approximation is the French œil region, or a rounded version of the "oy" in boy but kept front and short.

The English "ow" sound — the open-to-back glide of house — exists in Icelandic, but it is spelled á, not au. So au and á are different vowels, and confusing them swaps real words.

auga

eye — [ˈœyːɣa], 'ÖY-ga'; the au glides ö → y, lips rounded the whole way, NOT 'ow'

þau

they (neuter / mixed group) — [θœyː], 'thöy'; rhymes with nothing in English. Do NOT say 'thow'.

laun

wages, pay — [lœyːn], 'LÖYN'; the front-rounded glide again

þau vs þá

they [θœyː] vs then [θauː] — au is the front-rounded glide [œy], á is the English-style 'ow' [au]; one digraph apart in sound, totally different words

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au is [œy], a glide that stays FRONT and ROUNDED — start at Icelandic ö and slide toward i. It is never the English "ow" of house; that sound belongs to á. Drill au in isolation until your lips stay rounded all the way through.

ei and ey — identical twins, both [ei]

Icelandic ei and ey are pronounced exactly the same: [ei], a glide from [ɛ] up to [i], very close to the English "ay" in day (but cleaner, with less of an English off-glide). There is no audible difference between the two spellings whatsoever — they are perfect homophones. Which one a word uses is a matter of etymology and must be memorised letter by letter (handled on ei vs ey in Spelling).

Crucially, [ei] is not the English "eye" sound (the [aɪ] of my, time). English speakers often read ei as "eye" out of orthographic habit (think of German nein = "nine"). In Icelandic it is "ay," not "eye."

einn

one — [eiːtn̥], 'AYN' (with the special nn realisation); the ei is 'ay' as in day, never 'eye'

leið

way, route / leð (felt) — [leiːð], 'LAYTH'; ei = 'ay'

hey

hay — [heiː], 'HAY'; ey here is identical in sound to ei

þey

hush! (interjection) / calm — [θeiː], 'thay'; ey = [ei], the same sound as in leið

To feel the homophony directly, hold an ei word against an ey word and listen — they are acoustically the same vowel:

leið vs leyfa

route [leiːð] vs to allow [ˈleiːva] — the ei and the ey are pronounced identically [ei]; only the spelling differs

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ei and ey sound the same — [ei], like 'ay' in day. You cannot hear which spelling a word uses, so you must memorise it. And it is 'ay', not the English 'eye': Icelandic ei is never [aɪ].

The accented vowels are diphthongs too (a pointer)

For completeness: several of the accented letters are phonetically diphthongs, even though they are single letters with an acute accent. You will meet them constantly, so recognise them:

Letter	IPA	Glide	English-ish hint	Example
á	[au]	a → u (open to back)	"ow" as in house	þá (then)
ó	[ou]	o → u	"oh" as in go	sól (sun)
é	[jɛ]	j-glide → ɛ	"yeh"	fé (money, sheep)
æ	[ai]	a → i	"eye" as in my	læra (to learn)

Notice the trap this sets up: the English "eye" sound — which English speakers wrongly attach to ei — is actually Icelandic æ [ai]. And the English "ow" sound — which they wrongly attach to au — is actually á [au]. So two of the diphthongs English speakers most want to use go on the accented letters, not on the digraphs. Full detail on all six accented letters is on The Accented Vowels.

læra

to learn — [ˈlaiːra], 'LYE-ra'; æ is the 'eye' diphthong — this, not ei, is where 'eye' lives

þá

then — [θauː], 'thow'; á is the 'ow' diphthong — this, not au, is where 'ow' lives

Why au earns dedicated drilling

The distinguishing point: of all Icelandic sounds, au [œy] is the one that most reliably outs a foreign speaker, because it is acoustically front-rounded and has no English neighbour to lean on. Learners reach for the nearest familiar shape — English "ow" or "oh" — and land far away. The two corrective habits are: keep the lips rounded for the entire glide (do not let them spread), and keep the tongue forward (do not let it pull back as it would in "ow"). Start from a solid Icelandic ö, then glide up toward i without un-rounding. A sentence to practise the front-rounded glide in flow:

Þau eiga rauðan bíl og brúnt hús.

They own a red car and a brown house. — þau [θœyː] and rauðan [ˈrœyːðan] drill the au glide; note hús has ú (plain 'oo'), not au.

Common Mistakes

❌ þau — pronounced 'thow' like English 'how'

Incorrect — au is the front-rounded glide [œy], not English 'ow'. 'Thow' would be þá.

✅ þau — [θœyː], 'thöy', lips rounded throughout

they

❌ auga — pronounced 'OW-ga' (German/English ow)

Incorrect — [ˈœyːɣa]; the au stays front and rounded, gliding ö → y.

✅ auga — [ˈœyːɣa], 'ÖY-ga'

eye

❌ einn — pronounced 'EYEN' like English 'eye'

Incorrect — ei is 'ay' [ei] as in day, never the 'eye' diphthong. 'Eye' is æ.

✅ einn — [eiːtn̥], 'AYN'

one

❌ Assuming ei and ey sound different

Incorrect — they are exact homophones, both [ei]. The spelling must be memorised; the sound gives no clue.

✅ leið and hey both use [ei] — identical vowel, different spelling

route; hay

Key Takeaways

au = [œy], a front-rounded glide (ö → i) with no English equivalent — never the "ow" of house. This is the top accent giveaway; drill it with rounded lips throughout.
ei and ey are identical, both [ei] ("ay" as in day), and they are perfect homophones — spelling must be memorised. It is "ay," never the English "eye."
The "ow" sound English speakers want for au actually belongs to á [au]; the "eye" sound they want for ei actually belongs to æ [ai].
The accented letters á [au], ó [ou], é [jɛ], æ [ai] are phonetically diphthongs too — see The Accented Vowels.
Minimal pair to fix the digraph contrast: þau [θœyː] ("they") vs þá [θauː] ("then").

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