Strong masculine nouns are the single largest group in Icelandic, and they are where you meet the case system head-on. A noun counts as a strong masculine if its genitive singular ends in -s (occasionally -ar) and its nominative plural carries a real ending — -ar or -ir. These are the blunt, consonant-final words you learn first: hestur ("horse", kk), dagur ("day", kk), bíll ("car", kk), gestur ("guest", kk). This page lays out the shared template that all strong masculines follow, shows you how a single pair of forms sorts each word into its subclass, and hands you the one insight that makes the whole class click: the -ur you see in the dictionary is not part of the word — it is the nominative ending, and it falls away in every other case.
The shared template
Every strong masculine is built from a stem plus case endings. Take hestur: the stem is hest-, and the endings stack on top of it. Here is the full eight-cell paradigm, the model for the entire class:
| Case | Singular | Plural |
|---|---|---|
| Nefnifall (nom.) | hestur | hestar |
| Þolfall (acc.) | hest | hesta |
| Þágufall (dat.) | hesti | hestum |
| Eignarfall (gen.) | hests | hesta |
Read down the singular: hestur, hest, hesti, hests. The nominative adds -ur, the accusative is the bare stem hest, the dative adds -i, and the genitive adds -s. Read across to the plural: hestar, hesta, hestum, hesta — nominative -ar, accusative and genitive -a, dative -um. This template — -ur / – / -i / -s in the singular, -ar / -a / -um / -a in the plural — is the backbone of the most common subclass.
Hesturinn minn heitir Blesi.
My horse is called Blesi. Nominative singular 'hestur' — the dictionary form, with the -ur ending.
Ég gef hestinum hey á morgnana.
I give the horse hay in the mornings. Dative singular 'hesti' (here with the article, hestinum) — the -i dative.
The key insight: -ur is an ending, not the stem
Here is the fact most textbooks bury and most learners miss. In hestur, the -ur is the nominative singular ending. It is glued on for one case only. The actual word — the stem that carries the meaning — is hest-. That is why the accusative is hest and not hestur: you are not "shortening" the word, you are seeing it without its nominative ending for the first time.
Ég sá hest úti á túni.
I saw a horse out in the field. Accusative singular 'hest' — the bare stem, with the -ur of the nominative gone.
Þetta er bíll. Ég keypti bíl í gær.
This is a car. I bought a car yesterday. 'bíll' (nom.) vs 'bíl' (acc.) — the same stem, one with its ending and one without.
English has no equivalent of this. An English noun like "horse" is the same in every grammatical role — subject, object, after a preposition. Icelandic dresses the subject form in -ur and then undresses it for everything else, so the form you memorised from the dictionary is, paradoxically, the least representative of the word.
The nominative singular comes in several shapes
The nominative ending is usually -ur (hestur, dagur, gestur, hattur), but a few stems produce a different surface form:
- -l → -ll: a stem ending in -l doubles it: bíll ("car"), stóll ("chair"). The stem is still single-l (bíl-, stól-).
- -n → -nn: a stem ending in -n doubles it: steinn ("stone"), hreinn ("clean", as a name). The stem is single-n (stein-).
- -r → -r: some stems just add -r: hamar ("hammer"), or end in -ur that is part of the stem in a handful of words.
- -ill / -inn: words like lykill ("key") and himinn ("sky") lose their medial vowel in the oblique cases (lykli, himni).
Steinninn er þungur.
The stone is heavy. Nominative 'steinn' with the doubled -nn; the stem is 'stein-'.
Ég týndi lyklinum mínum.
I lost my key. Dative 'lykli' (here lyklinum, with the article) — the medial -i- of 'lykill' drops out before the ending.
Whatever the surface shape, the principle holds: that final cluster belongs to the nominative singular. Find the stem, and the rest of the paradigm is predictable.
How the genitive singular and nominative plural sort the class
A strong masculine's subclass is fixed by two forms together: the genitive singular and the nominative plural. These are the two forms a good dictionary gives you, precisely because they pin down everything else.
The two great plural classes are:
- -ar plural (the default, by far the largest): hestur → hestar, dagur → dagar, bíll → bílar. Genitive singular -s (hests, dags, bíls). This is the productive class — new loanwords join it.
- -ir plural: gestur → gestir, staður → staðir ("place"). Genitive singular also -s (gests, staðar — note staður takes -ar). The plural stem often shows i-umlaut.
Here is gestur for contrast with hestur — identical singular template, different plural:
| Case | Singular | Plural |
|---|---|---|
| Nefnifall (nom.) | gestur | gestir |
| Þolfall (acc.) | gest | gesti |
| Þágufall (dat.) | gesti | gestum |
| Eignarfall (gen.) | gests | gesta |
Við fáum gesti í kvöld.
We're having guests tonight. Accusative plural 'gesti' (from 'gestur') — the -ir class shows -i here, where the -ar class would show -a (hesta).
Margir gestir komu í veisluna.
Many guests came to the party. Nominative plural 'gestir' — the -ir plural that names this whole subclass.
The lesson is that you cannot predict the plural from the nominative singular alone. Both hestur and gestur end in -ur, but one pluralises in -ar and the other in -ir. You must learn the plural with the word — which is exactly why the dictionary citation gives you the genitive singular and the nominative plural as a pair.
The dative singular -i is real — don't drop it
English speakers reliably forget the dative singular -i because nothing in their language demands it. After many prepositions and as an indirect object, a strong masculine takes -i: á hesti ("on a horse"), frá bæ — note that not every word takes -i (some keep the bare stem), but where the -i belongs, leaving it off is an error a native speaker hears instantly.
Hún kom á hesti yfir ána.
She came across the river on a horse. Dative singular 'hesti' after 'á' — the -i is obligatory here.
Ég sagði þetta við gestinn, ekki við þig.
I said that to the guest, not to you. Accusative 'gest' (here gestinn) after 'við', which takes the accusative — contrast the dative 'hesti' above.
The dative plural -um and u-umlaut
Every strong masculine forms its dative plural in -um (hestum, gestum, bílum). When the stem vowel is a, that -um rounds it to ö — the u-umlaut. So dagur ("day") has the dative plural dögum, not dagum, and hattur ("hat") has höttum. This is not optional and not a typo: the a of the stem becomes ö whenever a syllable with u follows.
Á góðum dögum sést yfir allan fjörðinn.
On clear days you can see across the whole fjord. Dative plural 'dögum' (from 'dagur') — a → ö before the -um ending.
Hann gengur alltaf með húfu, aldrei með höttum.
He always wears a beanie, never hats. Dative plural 'höttum' (from 'hattur') — the same u-umlaut a → ö.
Common Mistakes
❌ Ég sá hestur.
Incorrect — the object is accusative, and the accusative drops the nominative -ur: 'hest'.
✅ Ég sá hest.
I saw a horse. Accusative 'hest' — bare stem, no -ur.
❌ Assuming gestur pluralises like hestur: 'margir gestar'
Incorrect — 'gestur' belongs to the -ir class: the plural is 'gestir', not 'gestar'. You can't read the plural off the -ur nominative.
✅ margir gestir
many guests — the -ir plural of 'gestur'.
❌ Dropping the dative -i: 'Hún kom á hest yfir ána'
Incorrect — 'á' + dative here needs the dative singular 'hesti', not the bare accusative 'hest'.
✅ Hún kom á hesti.
She came on a horse. Dative singular 'hesti'.
❌ No u-umlaut in the dative plural: 'á góðum dagum'
Incorrect — the -um dative plural rounds stem a → ö: 'dögum', not 'dagum'.
✅ á góðum dögum
on good days — dative plural 'dögum'.
❌ Keeping the double consonant in oblique cases: 'ég keypti bíll'
Incorrect — the -ll of 'bíll' is the nominative shape; the accusative is the single-l stem 'bíl'.
✅ Ég keypti bíl.
I bought a car. Accusative 'bíl' — single l.
Key Takeaways
- A masculine noun is strong if its genitive singular ends in -s (sometimes -ar) and its nominative plural in -ar or -ir.
- The -ur / -ll / -nn / -r of the nominative singular is an ending, not part of the stem — it disappears in every other case (hestur → stem hest-).
- The singular template is -ur / – / -i / -s (hestur, hest, hesti, hests); the plural is -ar / -a / -um / -a for the default class.
- The gen.sg + nom.pl pair sorts a word into its subclass; you cannot predict the plural from the nominative alone (hestur → hestar vs gestur → gestir).
- The dative singular -i is obligatory where it occurs — English speakers routinely drop it.
- The dative plural is -um, and a stem a rounds to ö by u-umlaut (dagur → dögum, hattur → höttum).
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Start learning Icelandic→Related Topics
- Strong Masculine: -ar Plural (hestur type)A2 — The largest and most productive strong masculine subclass — genitive singular -s, nominative plural -ar — drilled through hestur, dagur and the -ll/-nn stems bíll and steinn, with the u-umlaut in dögum and the bare oblique singular.
- Weak Masculine Nouns: -i type (tími, skóli)A2 — The weak masculine declension — nominative singular -i, all oblique singulars -a, nominative plural -ar — where accusative, dative and genitive singular collapse into one form (tíma), drilled through tími and skóli with the irregular bóndi → bændur.