Compounding glues whole words together; derivation reshapes a single root by adding a prefix or suffix. A teacher is kenna "teach" plus -ari; the impossible is mögulegt "possible" with the prefix ó-. This page catalogues the affixes that are actually productive in modern Icelandic — the ones you can apply to new roots and be understood — and singles out the most valuable of them all: the prefix ó-, which negates almost any adjective on sight. Master ó- and you roughly double your adjective vocabulary, because every positive instantly gives you its opposite.
Suffixes that make agents: -ari
The suffix -ari turns a verb into the person (or thing) that does it — the exact counterpart of English -er in teach → teacher. It is fully productive: give it a verb stem and you get the doer.
| Verb |
| Agent |
|---|---|---|
| kenna ('to teach') | kennari | teacher |
| baka ('to bake') | bakari | baker |
| spila ('to play') | spilari | player (also a device) |
Kennarinn minn í menntaskóla var algjör snillingur.
My teacher in upper-secondary school was an absolute genius. (kenna + -ari → kennari)
Bakarinn á horninu opnar klukkan sex á morgnana.
The baker on the corner opens at six in the mornings. (baka + -ari → bakari)
Agent nouns in -ari are masculine and decline like other weak masculines (kennari, kennara, kennara, kennara in the singular). Note that -ari attaches to the verb, so the doer of baka is bakari — not a noun-based form.
Suffixes that make abstract nouns: -ing, -un, -leiki, -skapur
A cluster of suffixes turns verbs and adjectives into abstract nouns — the -ness, -tion, -ity, -ship of Icelandic. You don't need to master the choice between them at B1, but you should recognise them, because they are everywhere.
| Suffix | From | Example | Meaning |
|---|---|---|---|
| -ing | verb | kenning (kenna) | theory, doctrine |
| -un | verb | könnun (kanna) | survey, investigation |
| -leiki | adjective | möguleiki (mögulegur) | possibility |
| -skapur | noun/adjective | vinskapur (vinur) | friendship |
Það er enginn möguleiki á því að klára þetta í dag.
There's no possibility of finishing this today. (mögulegur 'possible' → möguleiki 'possibility', via -leiki)
Vinskapur þeirra hefur enst í þrjátíu ár.
Their friendship has lasted thirty years. (vinur 'friend' → vinskapur 'friendship', via -skapur)
Suffixes that make adjectives: -legur, -laus, -samur
Three suffixes turn nouns (and verbs) into adjectives.
-legur is the great adjective-maker, the rough equivalent of English -ly/-al/-ish/-able — it forms an adjective meaning "having the quality of, characterised by." It is highly productive.
| Base |
| Adjective |
|---|---|---|
| vinur ('friend') | vinalegur | friendly |
| eðli ('nature') | eðlilegur | natural |
| barn ('child') | barnalegur | childish |
Afgreiðslukonan var rosalega vinaleg við okkur.
The shop assistant was incredibly friendly to us. (vinur 'friend' → vinalegur 'friendly', via -legur)
Það er alveg eðlilegt að vera kvíðinn fyrir próf.
It's completely natural to be anxious before an exam. (eðli 'nature' → eðlilegur 'natural')
-laus means "without X, lacking X" — the equivalent of English -less. It attaches to a noun and says the thing is absent.
| Noun |
| Adjective |
|---|---|---|
| von ('hope') | vonlaus | hopeless |
| atvinna ('employment') | atvinnulaus | unemployed |
| gagn ('use') | gagnslaus | useless |
Hann hefur verið atvinnulaus síðan í haust.
He's been unemployed since the autumn. (atvinna 'work' + -laus → 'without work')
Þetta er gjörsamlega vonlaust, við náum aldrei strætó.
This is utterly hopeless, we'll never catch the bus. (von 'hope' + -laus → 'hopeless')
-samur forms adjectives meaning "inclined to, full of X" — like English -ful/-some.
Hann er friðsamur maður sem forðast öll átök.
He's a peaceable man who avoids all conflict. (friður 'peace' → friðsamur 'peaceable', via -samur)
Prefixes
ó- : the negation prefix, and your single most valuable affix
ó- is the Icelandic un-/in-/im-: it negates the word it attaches to, turning a positive into its opposite. And it is fully productive — it stacks on almost any adjective (and a great many nouns and adverbs). This is the headline of the whole page. If you know the positive, the prefix ó- hands you the negative for free.
| Positive |
| Negative |
|---|---|---|
| mögulegur ('possible') | ómögulegur | impossible |
| þægilegur ('comfortable') | óþægilegur | uncomfortable |
| hamingjusamur ('happy') | óhamingjusamur | unhappy |
| dýr ('expensive') | ódýr | cheap (in-expensive) |
Það er alveg ómögulegt að fá miða á þennan tónleika.
It's completely impossible to get a ticket to this concert. (mögulegur → ómögulegur)
Þessir skór eru óþægilegir, ég fæ blöðrur.
These shoes are uncomfortable, I'm getting blisters. (þægilegur → óþægilegur)
Hann var óhamingjusamur í gamla starfinu og sagði upp.
He was unhappy in his old job and quit. (hamingjusamur → óhamingjusamur)
and- : counter-, against
and- marks opposition or reciprocity — "counter-, anti-, response."
Hún andaði djúpt og fann andstöðu hópsins gegn tillögunni.
She breathed deeply and felt the group's opposition to the proposal. (and- + staða 'position' → andstaða 'opposition')
endur- : re-, again
endur- is the Icelandic re-: do it again, restore.
Við þurfum að endurskoða samninginn fyrir mánudag.
We need to review (lit. re-look-at) the contract before Monday. (endur- + skoða → endurskoða 're-examine')
van- : mis-, under-, lacking
van- signals deficiency or going wrong — "under-, mis-, lacking."
Barnið er vannært og þarf að komast undir læknishendur.
The child is undernourished and needs medical attention. (van- + nærð(ur) → vannærður 'undernourished')
for- and frum- : fore-/pre- and proto-/primal
for- is "fore-, pre-, ahead" (forseti "president," literally "fore-sitter"; formaður "chairman"); frum- is "proto-, primal, original" (frumkvöðull "pioneer," frumstæður "primitive").
Forseti Íslands ávarpaði þjóðina á nýársdag.
The President of Iceland addressed the nation on New Year's Day. (for- 'fore' + seti 'sitter' → forseti)
Hún er frumkvöðull í íslenskri tækni.
She's a pioneer in Icelandic technology. (frum- 'proto/original' + kvöðull → frumkvöðull)
English vs Icelandic derivation
The mechanics will feel familiar — Icelandic -ari is English -er, ó- is un-/in-, -laus is -less, endur- is re- — but two differences matter. First, Icelandic derivation is more regular and transparent: ó- attaches cleanly to almost any adjective, whereas English negation is a lottery between un- (unhappy), in- (impossible), dis- (dishonest), and non-. You rarely have to choose in Icelandic — ó- covers the field. Second, the derived word keeps its native shape and accent: ó- always carries the acute (ómögulegt), and agent nouns build off the verb (bakari from baka), not a Latinate root.
Common Mistakes
❌ Það er omögulegt að klára þetta í dag.
Wrong — the negation prefix is ó-, with the acute accent: ómögulegt.
✅ Það er ómögulegt að klára þetta í dag.
It's impossible to finish this today.
The prefix is ó-, never bare o-. Dropping the accent changes a real letter; omögulegt is a misspelling.
❌ Það er ekki mögulegt að fá miða (reaching for ekki when ó- exists).
Not wrong, but a learner who doesn't know ó- misses the natural ómögulegt.
✅ Það er ómögulegt að fá miða.
It's impossible to get a ticket.
This is the productivity insight as a trap: a learner who never internalises ó- circumlocutes with ekki mögulegt and misses ómögulegt. Know the positive, prefix ó-, get the negative.
❌ Hún er bakkona / bökari.
Wrong — the agent of baka is bakari (verb + -ari).
✅ Hún er bakari.
She's a baker.
Agent nouns are built from the verb stem + -ari: baka → bakari. (Note bakari is masculine even for a woman in the neutral term.)
❌ vonalaus
Wrong stem-join — it is vonlaus, von + -laus.
✅ vonlaus
hopeless (von 'hope' + -laus 'without')
-laus attaches to the bare noun von: vonlaus, not vonalaus.
Key Takeaways
- -ari makes agents from verbs (kenna → kennari, baka → bakari), like English -er.
- -ing/-un/-leiki/-skapur make abstract nouns (möguleiki, vinskapur) — recognise them, even if you don't yet choose between them.
- -legur is the great adjective-maker (vinalegur, eðlilegur); -laus = "without" (vonlaus); -samur = "inclined to" (friðsamur).
- ó- productively negates almost any adjective and doubles your vocabulary (þægilegur → óþægilegur) — and keeps its accent.
- Useful prefixes: and- (counter-), endur- (re-), van- (mis-/under-), for- (fore-/pre-), frum- (proto-/primal).
Now practice Icelandic
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Start learning Icelandic→Related Topics
- Compounding: The Core Word-Building EngineB1 — How Icelandic compounds are built structurally — a determinant (first element) modifies a head (last element), the head fixes gender and inflection, and the elements join with a bare link, a genitive -s link, or a genitive plural -a link (sólskin, landsbanki, barnabók), often encoding a hidden grammatical relationship you can read off.
- Nominalisation: Making Nouns from Verbs and AdjectivesB2 — How Icelandic builds nouns out of verbs and adjectives. Deverbal nouns in -ing/-un name the action (bygging 'building', skoðun 'examination'); the -andi present participle nominalises as an agent (nemandi 'student', stjórnandi 'director'); and DEADJECTIVAL abstracts in -leiki/-d/-t/-ð name the quality (fegurð 'beauty', hæð 'height', lengd 'length'). The headline insight: deadjectival abstracts systematically trigger i-umlaut (hár→hæð, langur→lengd, breiður→breidd, djúpur→dýpt) — the very same vowel change as the comparative — so the abstract noun and the comparative share a vowel. Build native nouns instead of importing English '-tion' words.
- Word Formation: Compounding, Derivation, CoinageB1 — How Icelandic builds new words almost entirely from native material — prolific compounding, affix derivation, and the deliberate coinage of transparent neologisms (sími, tölva, þota) driven by linguistic purism (málrækt) — so vocabulary grows internally and is largely decodable from its roots.
- Suffix Catalogue: -legur, -laus, -samur, -leiki, -skapurB1 — A working catalogue of the productive Icelandic derivational suffixes — adjective-makers -legur ('-ly/-ish': vinalegur 'friendly'), -laus ('-less': atvinnulaus 'unemployed'), -samur ('-some/prone to': friðsamur 'peaceable'), -ugur (grösugur 'grassy'); and noun-makers -leiki/-leikur (abstract: kærleikur 'love'), -skapur (abstract/collective: vinskapur 'friendship'), -ari (agent: kennari 'teacher'), -ing/-un (deverbal) — each paired with its English analogue and tagged for the resulting word class.
- Prefix Catalogue: ó-, and-, endur-, van-, sam-B1 — A working catalogue of the productive Icelandic prefixes — ó- (negation: óþarfur 'unnecessary'), and- (counter/against: andstæða 'opposite'), endur- (re-: endurtaka 'repeat'), van- (under/mis-: vanmeta 'underestimate'), sam- (co-/together: samvinna 'cooperation'), for- (pre-/fore-: forseti), mis- (mis-: misskilja 'misunderstand'), gagn- (counter/through: gagnrýni 'criticism') — each mapped onto its English/Latin analogue so you can decode and build words on sight.
- Negation: ekki and Its PlacementA1 — The core negator ekki 'not' and where it sits — after the finite verb in a main clause, after a pronoun object but before a full-noun object — making ekki the diagnostic of Icelandic clause architecture, plus a first look at enginn, aldrei, and ekkert.