Strong feminine nouns are the ones whose genitive singular ends in a consonant + -ar (or, in a smaller group, -ur / -r), and whose plurals carry a real ending — -ir or -ar. They are the feminine counterpart to the strong masculines and neuters, and they hide a surprise for English speakers: most of them are not the friendly -a words you might expect. They are blunt, consonant-final monosyllables like borg ("city"), bók ("book"), mynd ("picture") and hönd ("hand"). This page lays out the strong feminine pattern, its subclasses (sorted by plural), and the single most useful fact about them: in the singular they barely move, so all the learning effort belongs in the plural.
The defining feature: the genitive -ar
What makes a feminine noun strong is the genitive singular in -ar (or -ur/-r). Everything else in the singular tends to be the bare stem. Take borg ("city"), the model strong feminine:
| Case | Singular | Plural |
|---|---|---|
| Nefnifall (nom.) | borg | borgir |
| Þolfall (acc.) | borg | borgir |
| Þágufall (dat.) | borg | borgum |
| Eignarfall (gen.) | borgar | borga |
Look down the singular column: borg, borg, borg, borgar. Three of the four cases are the identical bare stem; only the genitive borgar differs. This is the hallmark of the strong feminine — a nearly invariant singular with the -ar genitive sticking out as the only marker.
Reykjavík er stór borg.
Reykjavík is a big city. Nominative singular 'borg' — the bare stem.
Ég bý í borg.
I live in a city. Dative singular 'borg' — identical to the nominative; the preposition 'í' takes the dative here but the form doesn't change.
Íbúar borgarinnar eru margir.
The city's inhabitants are many. Genitive singular 'borgar' (+ article 'innar') — the one singular case that shows an ending.
The subclasses, sorted by plural
Strong feminines split into types by their plural, not their singular. The three you meet first:
The -ir plural type: borg, mynd, ferð
The largest group. Genitive singular -ar, plural in -ir. Models: borg → borgir, mynd → myndir ("picture"), ferð → ferðir ("trip/journey").
Ég tók margar myndir í ferðinni.
I took many pictures on the trip. Plural 'myndir' (from 'mynd') — the -ir plural.
Hún fer í tvær ferðir á ári.
She takes two trips a year. 'ferðir' — accusative plural, identical to the nominative plural (as always in this class).
The -ar plural type: á, brú
A smaller group whose plural is -ar rather than -ir, often with a short stem. Model: á ("river"), and brú → brýr ("bridge", with umlaut). Here is á in full — note the genitive singular ár and the dative plural ám:
| Case | Singular | Plural |
|---|---|---|
| Nefnifall (nom.) | á | ár |
| Þolfall (acc.) | á | ár |
| Þágufall (dat.) | á | ám |
| Eignarfall (gen.) | ár | áa |
Það er brú yfir ána.
There is a bridge over the river. 'ána' is the accusative singular of 'á' with the definite article — the bare 'á' plus '-na'.
Margar ár renna til sjávar.
Many rivers run to the sea. Plural 'ár' — note it is identical to the genitive singular 'ár', a common collision in short strong feminines.
The heavily umlauting monosyllables: bók, hönd
The group that punishes guessing. The plural fronts or rounds the stem vowel by i-umlaut. The classics: bók → bækur (ó → æ) and hönd → hendur (ö → e). These take a -ur plural, not -ir.
| Case | Singular (bók) | Plural (bók) |
|---|---|---|
| Nefnifall (nom.) | bók | bækur |
| Þolfall (acc.) | bók | bækur |
| Þágufall (dat.) | bók | bókum |
| Eignarfall (gen.) | bókar | bóka |
The singular is the usual quiet bók, bók, bók, bókar — but the nominative/accusative plural detonates into bækur, with ó → æ. There is no shortcut: you must learn that bók umlauts. The dative plural bókum and genitive plural bóka keep the original ó, because the umlaut is triggered only by the -ur plural ending.
Ég er að lesa góða bók.
I'm reading a good book. Singular 'bók' — bare stem, no umlaut.
Ég hef lesið margar bækur um Ísland.
I've read many books about Iceland. Plural 'bækur' with the i-umlaut ó → æ — the form that trips everyone.
Hún heldur á tveimur bókum.
She is holding two books. Dative plural 'bókum' — back to 'ó', because only the -ur nom./acc. plural triggers the umlaut.
Ég þvæ mér um hendurnar.
I wash my hands. Plural 'hendur' (from 'hönd') — ö → e umlaut, with the definite article '-nar'.
The dative plural -um and its rounding
Every strong feminine forms its dative plural in -um (borgum, bókum, ám). When the stem vowel is a, that -um rounds it to ö — the u-umlaut — exactly as in the neuters and elsewhere. So a strong feminine with an a will show ö in the dative plural even if its nominative plural does not.
Hún býr í einni af stærstu borgum landsins.
She lives in one of the country's biggest cities. 'borgum' — dative plural in -um (no a in the stem, so no rounding here).
Það eru margar leiðir milli bæjanna.
There are many roads between the towns. 'leiðir' (from 'leið', way/route) is another -ir strong feminine; note 'milli' + genitive 'bæjanna'.
Common Mistakes
❌ Assuming a feminine noun must end in -a: treating 'borg' as if it were weak
Incorrect — most strong feminines are consonant-final monosyllables (borg, bók, mynd, hönd). The -a ending marks WEAK feminines, a different class.
✅ borg, borg, borg, borgar (strong feminine)
city — consonant-final, with the -ar genitive. Strong, not weak.
❌ Dropping the genitive -ar: 'íbúar borgar' written as 'íbúar borg'
Incorrect — the genitive singular of a strong feminine adds -ar; the bare stem is nom./acc./dat. only.
✅ íbúar borgarinnar
the city's inhabitants — genitive 'borgar' (+ article).
❌ Forgetting the plural umlaut: 'margar bókur' for 'many books'
Incorrect — 'bók' umlauts in the nom./acc. plural: ó → æ, giving 'bækur'.
✅ margar bækur
many books — the i-umlaut plural 'bækur'.
❌ Carrying the umlaut into the dative plural: 'með bækum'
Incorrect — the umlaut is confined to the nom./acc. plural; the dative plural keeps the base vowel: 'bókum'.
✅ með tveimur bókum
with two books — dative plural 'bókum', back to ó.
❌ Giving 'borg' an -ir genitive by analogy with the plural: 'til borgir'
Incorrect — the -ir ending is the PLURAL; the genitive singular is 'borgar'. 'til' takes the genitive singular here.
✅ til borgar
to/towards the city — genitive singular 'borgar'.
Key Takeaways
- A feminine noun is strong if its genitive singular ends in -ar (or -ur/-r) — not in a vowel.
- The singular is nearly invariant: nom. = acc. = dat. = bare stem; only the genitive -ar stands out (borg, borg, borg, borgar).
- Subclasses are sorted by plural: the -ir type (borg → borgir, mynd → myndir), the -ar type (á → ár), and the umlauting monosyllables (bók → bækur, hönd → hendur).
- The i-umlaut lives only in the nominative/accusative plural; the dative plural keeps the base vowel (bækur but bókum).
- The dative plural is always -um, and an a-stem rounds it to ö by u-umlaut.
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- Strong Feminine: -ir Plural (borg, mynd)A2 — The largest strong feminine subclass — genitive singular -ar, nominative plural -ir — where the singular is almost invariant (borg/borg/borg/borgar) and only the genitive and the whole plural ever change, drilled through borg and mynd.
- Weak Feminine Nouns: -a type (kona, gata)A2 — The weak feminine declension — nominative singular -a, all oblique singulars -u, nominative plural -ur — drilled through kona and gata, with the u-umlaut a→ö (götum) and the suppletive genitive plural kvenna.