Vowel shifts in Icelandic
Two main types of vowel shift: U-umlaut (a → ö) and I-umlaut (multiple vowel correspondences).
They show up regularly in declension, conjugation, and word formation.
Two types of umlaut
U-umlaut (mutation triggered by -u)
The vowel a → ö under the influence of a u in a suffix or ending.
I-umlaut (mutation triggered by -i / -j)
Multiple vowel correspondences (a→e, á→æ, ó→æ, u→y, etc.), caused by a historical i or j.
A bit of history Note
U-umlaut arose under the influence of the vowel u in the following syllable — the vowel of the preceding syllable was "pulled" toward the articulation of u.
I-umlaut (i-mutation) arose in the same way under the influence of i / j — the front articulation of i pushed the stem vowel forward.
Although the trigger sounds themselves have often long since disappeared from the language, the alternations survive as part of the grammatical system.
Where vowel shifts occur
Declension: a-stems — dat.pl., gen.pl., neuter plural
Conjugation: imperative, pres. 1pl/3pl of verbs in -a
Comparative: langur → lengri, fágætur → fágættari
Word formation: land → lendi, brjóst → brysti
U-umlaut (a → ö)
The vowel a changes to ö if the following syllable
contains, or historically contained, the sound u.
The basic rule U
a → ö before a suffix/ending containing u.
U-umlaut is triggered by a u standing immediately after the stem vowel — it cannot skip over another vowel.
hattur (hat, nom.sg.) → dat.pl. höttum
saga (story) → 1pl við sögum
kalla (to call) → 1pl við köllum
The key exception: nom.sg.masc. -ur Exception
The ending -ur of the masculine nom.sg. does NOT trigger U-umlaut.
dagur (day), not *dögur
svartur (black), not *svörtur
fastur (firm), not *föstur
But in all other u-umlaut forms it works as expected:
dagur → dat.pl. dögum, nom.pl. dagar
svartur → fem.sg. svört, neut.sg. svart
Nouns Rule
In forms where u follows the stem: dat.pl., gen.pl., neuter plural.
land → pl. lönd
barn → pl. börn
maður → dat.pl. mönnunum
jökull → nom.pl. jöklar (from *jakull)
Verbs Rule
Verbs in -a get ö in the forms where the thematic vowel changes to u.
ég kallaði → við kölluðum
ég sagði → við sögðum
ég talaði → við tölum (irregular, a→ö in the stem)
U-umlaut: Examples
Concrete examples of the a → ö shift in various words and forms.
Direct examples (a → ö) U
| Base form |
Form with -u- |
Meaning |
| hattur |
höttum (dat.pl.) |
hat |
| saga |
sögum (1pl) |
story; to tell |
| land |
lönd (pl.) |
land |
| barn |
börn (pl.) |
child |
| kalla |
köllum (1pl) |
to call |
| fara |
förum (1pl) |
to go, to leave |
| langur |
löng (fem.) |
long |
Reverse examples (ö → a) Exception
In some words the stem vowel ö alternates with a when the ending has no u.
| Form with ö |
Form with a |
Note |
| gjöf (nom.sg.) |
gjafar (gen.sg.) |
gift |
| fjörður (nom.sg.) |
fjarðar (gen.sg.) |
fjord |
| köttur (nom.sg.) |
kattar (gen.sg.) |
cat |
| sonur (nom.sg.) |
syni (dat.sg.) |
son (I-umlaut in dat.) |
Loanwords Note
U-umlaut also applies in loanwords, as long as the stem contains an a.
| Sg. |
Pl. |
Source |
| ball |
böll |
Eng. ball |
| gramm |
grömm |
international |
| sónata |
sónötur |
Ital. sonata |
U-umlaut: Advanced rules
Tricky cases: several syllables with a, vanished trigger sounds, loanwords with double a.
The vanished trigger sound Rule
U-umlaut is triggered by a u in the immediately following syllable. Even if that u has long since dropped out of the language, the vowel shift remains.
It cannot skip over a vowel: if another vowel stands between the a and the u, no umlaut takes place.
*han-u-r → hönn (the lost u triggered the shift)
fatlaður — the stem is "fat", but a does not become ö before i (different types)
Two syllables with "a" Important
Native words: the first a → ö, the second a → u.
gamall (old, masc.) → fem. gömul
kalasti → kölustu
Loanwords: the second a → u, the first a stays.
japanskur (Japanese, masc.) → fem. japönsk
*(here there is only one a in the stem and one a in the suffix)*
Suffix a → u Rule
In many verb forms, an a in the suffix changes to u, which in turn triggers U-umlaut in the stem.
ég kallaði → við kölluðum
Suffix -aði → -uðum, stem kall- → köll-
ég sagði → við sögðum
Suffix -i → -um, stem sag- → sög-
I-umlaut (mutation triggered by -i/-j)
The stem vowel changes under the influence of a historical i or j in the following syllable.
Unlike U-umlaut, there are many vowel correspondences here.
The essence of I-umlaut I
I-umlaut moves the articulation of the vowel forward and up — toward the position of [i].
The trigger was a historical i or j (yod). The trigger sound itself has often already disappeared.
This is the most widespread type of alternation in Icelandic: comparatives, the imperative, weak nouns, the plural of many words.
The most frequent correspondences Memorize
| Stem |
|
Result |
Example |
| a |
→ |
e |
fara → fer (imp.) |
| á |
→ |
æ |
láta → læt (imp.) |
| ó |
→ |
æ |
fórum → færi (subj.) |
| ú |
→ |
ý |
súpa → sýp (imp.) |
| u |
→ |
y |
brutum → bryti (subj.) |
Where I-umlaut shows up
Imperative: fara → farðu / ferðu (both variants)
Comparative: hár → hærri, stór → stærri
Plural: maður → menn (people)
Subjunctive: fórum → færi
Word formation: fjörður → firðir (pl.), spónn → spænir