einn: 'one', 'a certain', and the (non-)Indefinite Article | Icelandic Grammar

English speakers meeting Icelandic almost always make the same mistake with einn: they treat it as the word for "a/an." It is not. Icelandic has no indefinite article — a bare noun already means "a book," "a man." So what is einn? It is three overlapping things: the numeral "one," a fully-declined determiner meaning "a certain" (used to introduce a referent into a story), and a plural form meaning "some" or "a pair of." Knowing when einn genuinely belongs — and when it sounds like you are pointedly counting — is the whole game here.

einn declines: einn / ein / eitt

Unlike English "one," which never changes, einn agrees with its noun in gender, number, and case, following the strong adjective pattern. The three nominative singular forms are the ones to fix first: einn (masc.), ein (fem.), eitt (neut.). Note the spelling: masculine einn has a double n, neuter eitt has a double t.

	Masc.	Fem.	Neut.
Nom.	einn	ein	eitt
Acc.	einn	eina	eitt
Dat.	einum	einni	einu
Gen.	eins	einnar	eins

Ég á einn hest, eina kú og eitt lamb.

I have one horse, one cow and one lamb. (einn masc. / eina fem. acc. / eitt neut. — agreeing with each animal)

Hann kom með einni vinkonu.

He came with one (female) friend. (einni = fem. dative, after the preposition 'með')

einn as the numeral "one"

The bedrock use: counting. When you mean the number one — one as opposed to two or three — you use einn, and it agrees with what you are counting. This is the use where einn is never optional.

Það er bara einn miði eftir.

There's only one ticket left. (einn = the number, masc. to match miði)

Ég bað um eitt glas, ekki tvö.

I asked for one glass, not two. (eitt = neuter 'one', contrasted with tvö 'two')

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If you could replace the English word with "a single / exactly one" and the contrast with other numbers survives, you want the numeral einn. If you could drop "a" entirely and the sentence still means the same, you do not want einn — use the bare noun.

einn as "a certain": introducing a referent

Here is the subtle, genuinely article-like use. Einn can introduce a specific but as-yet-unidentified person or thing into the discourse — English "a certain," "this one," "some" (as in "some guy phoned"). You are not counting; you are flagging a particular referent the listener has not met yet but that matters to the story.

Einn maður kom og spurði um þig.

A (certain) man came and asked about you. (einn introduces a specific man you don't yet know)

Ég þekki eina konu sem talar sjö tungumál.

I know a (certain) woman who speaks seven languages. (eina = a specific woman, introduced into the conversation)

Crucially, this is not wrong — it is idiomatic and very common. The error is not using this einn; the error is overusing it, slapping it on every indefinite noun the way English forces "a/an." The "a certain" einn carries a flavour of "a particular one I have in mind"; if every "a" in your speech comes out as einn, native ears hear constant, pointless specificity.

Einu sinni var einn kóngur sem átti þrjár dætur.

Once upon a time there was a king who had three daughters. (the classic fairy-tale opener — einn introduces the king)

That last sentence is the prototype: einu sinni var einn … is the standard Icelandic fairy-tale opening, exactly where English uses "once upon a time there was a …" Einn here is doing genuine article-like work, introducing the protagonist. Storytelling is the home turf of "a certain" einn.

The line between "a" and "one": a test

Because the same form can mean the bland "a" or the pointed "one," learners need a reliable way to choose. Ask whether you are contrasting with other numbers or introducing a particular referent:

You mean…	Use	Example
plain "a/an" (no emphasis)	bare noun	Ég sá hund. (I saw a dog.)
"a certain / some particular"	einn + noun	Einn hundur elti mig. (A [certain] dog chased me.)
the number "one" (vs two, three)	einn + noun	Bara einn hundur, ekki tveir. (Only one dog, not two.)

Ég sá hund í garðinum.

I saw a dog in the garden. (neutral 'a dog' — bare noun, no einn)

Einn hundur elti mig alla leið heim.

A (certain) dog chased me all the way home. (einn introduces a specific dog into the story)

The difference between the first sentence and the second is real and felt by natives: the first just reports seeing a dog; the second foregrounds a particular dog you are about to say more about.

The plural: einir / einar / ein meaning "some" or "a pair of"

Although "one" has no plural in logic, einn does have plural forms — einir (masc.), einar (fem.), ein (neut.) — and they are not contradictory: they mean "some," "a pair of," or "a set of." Their most important everyday job is with plural-only nouns (nouns that have no singular, like buxur "trousers," skæri "scissors," gleraugu "glasses"). To say "a pair of trousers" you cannot use singular einn, so the plural einar steps in.

Ég þarf að kaupa einar buxur.

I need to buy a pair of trousers. (einar = fem. pl., because 'buxur' is a plural-only noun)

Áttu ein gleraugu sem ég má fá lánuð?

Do you have a pair of glasses I could borrow? (ein = neut. pl. with the plural-only 'gleraugu')

Þeir voru einir í húsinu.

They were alone in the house. (einir, masc. pl. — here meaning 'alone/by themselves')

So the plural einar buxur is genuinely "one pair," counting pairs; and einir/einar can also drift toward "alone, by themselves," as in the last example. Either way, the plural of einn is a real, needed form — it is how Icelandic counts items that come only in the plural.

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For plural-only nouns (buxur, skæri, gleraugu, dyr), "a/one pair of" forces the plural einar/einir/ein. There is no singular option: ein buxa is not a word.

Common Mistakes

❌ Ég vil kaupa einn bíl. (just meaning 'a car')

Misleading — this sounds like 'one car' (counting). For neutral 'a car', use the bare noun.

✅ Ég vil kaupa bíl.

I want to buy a car. (bare noun = 'a car')

The single biggest error: using einn as a routine English "a/an." The bare noun already means "a"; einn adds "one (specifically)."

❌ Einu sinni var ein kóngur.

Incorrect — 'kóngur' is masculine, so it takes the masculine 'einn', not feminine 'ein'.

✅ Einu sinni var einn kóngur.

Once upon a time there was a king. (masc. einn for masc. kóngur)

Einn must agree in gender: einn maður (m.), ein kona (f.), eitt barn (n.).

❌ Ég þarf að kaupa eina buxur.

Incorrect — 'buxur' is plural-only, so it needs the plural 'einar', not the singular feminine 'eina'.

✅ Ég þarf að kaupa einar buxur.

I need to buy a pair of trousers. (plural einar for the plural-only noun)

Plural-only nouns force the plural of einn; the singular form is ungrammatical with them.

❌ Ég á ein hest.

Incorrect — 'hestur' is masculine, so 'one horse' is 'einn hestur' (double n), not neuter 'eitt' or feminine 'ein'.

✅ Ég á einn hest.

I have one horse. (masc. einn, acc. einn)

Match the form to the noun's gender, and mind the spelling: masculine einn has a double n, neuter eitt a double t.

❌ Hann kom með ein vinkonu.

Incorrect — after 'með' the noun is dative, so the feminine dative is 'einni'.

✅ Hann kom með einni vinkonu.

He came with one (female) friend. (fem. dative einni after 'með')

Einn takes case too: the preposition með assigns dative, so the feminine form is einni, not nominative ein.

Key Takeaways

Icelandic has no indefinite article; a bare noun means "a." Do not use einn as a default "a/an."
Einn declines and agrees: einn (m.) / ein (f.) / eitt (n.) — double n in masculine, double t in neuter.
It has three live uses: the numeral "one," the "a certain" referent-introducer (idiomatic in storytelling — einu sinni var einn kóngur), and the plural "some / a pair of."
The "a certain" use is not an error — overusing it as English "a/an" is. It flags a particular referent you have in mind.
The plural einar/einir/ein is required with plural-only nouns: einar buxur "a pair of trousers."

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