Ordinal Numbers: fyrsti, annar, þriðji ... | Icelandic Grammar

Cardinals tell you how many (þrír "three"); ordinals tell you which in order (þriðji "third"). And where the cardinals were a special class with their own quirks, the ordinals are blessedly ordinary: they are simply adjectives, and they take the weak endings you already know from gamli maðurinn. They agree with their noun in gender, number and case. There is exactly one troublemaker — annar "second," which refuses to behave like the others — and we'll give it the attention it deserves. You'll need ordinals constantly for dates, floors and rankings, so they're worth nailing early.

The ordinals 1st-10th

#	Ordinal (m. sg.)	#	Ordinal (m. sg.)
1st	fyrsti	6th	sjötti
2nd	annar	7th	sjöundi
3rd	þriðji	8th	áttundi
4th	fjórði	9th	níundi
5th	fimmti	10th	tíundi

Notice that all of these except annar end in -i — fyrsti, þriðji, fjórði, fimmti, sjötti, sjöundi … — which is the masculine singular weak adjective ending. That is your visual cue that ordinals are weak adjectives. Watch the ð in þriðji and fjórði; it is part of the spelling, not a typo.

fyrsti dagurinn í vinnunni

the first day at work — fyrsti, weak, agreeing with masculine dagurinn.

Þetta er þriðja húsið frá horninu.

This is the third house from the corner. — þriðja, weak, agreeing with neuter húsið.

Hún varð fimmta í keppninni.

She came fifth in the competition. — fimmta, feminine.

Ordinals decline like weak adjectives

Because they are weak adjectives, ordinals change their ending to agree with the noun's gender and case. The weak endings are the small set you know: masculine -i, feminine and neuter -a in the nominative, and -a/-u across the obliques. Take fjórði "fourth":

Case	Masculine	Feminine	Neuter
Nominative	fjórði	fjórða	fjórða
Accusative	fjórða	fjórðu	fjórða
Dative	fjórða	fjórðu	fjórða
Genitive	fjórða	fjórðu	fjórða

Ég bý á þriðju hæð.

I live on the third floor. — hæð is feminine, dative after á; weak feminine þriðju.

Þetta gerðist á fjórða degi.

This happened on the fourth day. — dative masculine fjórða.

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Since ordinals are inherently definite-feeling ("the third house"), they take weak endings essentially everywhere — you almost never need a strong ordinal form. If you know the weak adjective endings, you know how to inflect fyrsti, þriðji, fjórði and all the rest. The one verb you must memorise separately is annar.

annar — the irregular 'second'

Here is the exception. annar "second" (also "other, another") is not a weak adjective with an -i ending — it is strong and irregular, and you must learn its forms outright. It looks nothing like the cardinal tveir, and there is no regular -th-style form like *annaði; that word does not exist.

Case	Masculine	Feminine	Neuter
Nominative	annar	önnur	annað
Accusative	annan	aðra	annað
Dative	öðrum	annarri	öðru
Genitive	annars	annarrar	annars

The vowel jumps around dramatically — a in annar/annan/annað, ö in önnur/öðrum/öðru, and a bare stem in aðra/aðrar. The doubled r in the feminine annarri/annarrar is also load-bearing. (The same word doubles as the pronoun "other/another," covered in full on the annar page; here we only need its ordinal use.)

annar dagurinn í röð með rigningu

the second day in a row with rain — masculine annar.

Hún á heima á annarri hæð.

She lives on the second floor. — hæð is feminine dative → annarri.

Þetta er í annað sinn sem ég kem hingað.

This is the second time I've come here. — neuter annað with sinn.

Dates use ordinals — and the '.' is the ordinal

Icelandic dates are built on ordinals: fimmti júní "the fifth of June," þriðji mars "the third of March." Crucially, when you write a date with digits, the period after the numeral is the ordinal marker — 5. júní is read aloud as fimmti júní, and 3. mars as þriðji mars. That little dot silently stands for a fully declined ordinal, which must agree with the (masculine) word dagur "day" that's understood behind it.

þriðji mars / 3. mars

the third of March — the '.' in 3. is read as the ordinal þriðji.

Afmælið mitt er annar júní.

My birthday is the second of June. — note: 'second' is annar, not a -th form.

Fundurinn er á fimmta degi mánaðarins.

The meeting is on the fifth day of the month. — dative fimmta after á.

When a date appears with the preposition þann or in an oblique case, the ordinal declines accordingly — þann fimmta júní "on the fifth of June" keeps the accusative fimmta. The takeaway for reading aloud: a written 5. is never just "five"; it is a declined fimmti/fimmta whose ending depends on the sentence around it.

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A written date hides a declined ordinal. 5. júní is not "five June" — it is fimmti júní, an ordinal agreeing with the unspoken masculine dagur. So when you read dates aloud, you must supply the right ordinal form, not the cardinal fimm.

Sequence and ranking phrases

Ordinals power a family of everyday fixed phrases, especially with sinn "time/occasion" (neuter):

Ég sá norðurljósin í fyrsta sinn í gærkvöldi.

I saw the northern lights for the first time last night. — í fyrsta sinn (accusative neuter).

Í fyrsta lagi er það of dýrt, í öðru lagi höfum við ekki tíma.

Firstly it's too expensive, secondly we don't have time. — í fyrsta lagi / í öðru lagi (note öðru, the neuter dative of annar).

Common Mistakes

❌ Afmælið mitt er tveir júní.

Incorrect — dates use the ordinal, not the cardinal; and 'second' is annar: annar júní.

✅ Afmælið mitt er annar júní.

My birthday is the second of June.

❌ í annaði sinn

Incorrect — there is no regular form *annaði; the ordinal 'second' (neuter) is annað: í annað sinn.

✅ í annað sinn

for the second time

❌ Hún býr á þriðja hæð.

Incorrect — hæð is feminine, so the weak ordinal is þriðju, not þriðja: á þriðju hæð.

✅ Hún býr á þriðju hæð.

She lives on the third floor.

❌ á annari hæð

Incorrect spelling — the feminine dative of annar doubles the r: annarri.

✅ á annarri hæð

on the second floor

Key Takeaways

Ordinals are weak adjectives: fyrsti, þriðji, fjórði, fimmti, sjötti, sjöundi, áttundi, níundi, tíundi — all ending in -i in the masculine, agreeing with their noun.
annar "second" is the exception: strong and irregular — annar/annan/öðrum/annars, f önnur/aðra/annarri/annarrar, n annað. No *annaði exists.
Dates use ordinals, and the written '.' is the ordinal: mars
= þriðji mars; read aloud with the correctly declined form.
Watch the ð in þriðji, fjórði and the doubled r in annarri/annarrar.
Common fixed phrases: í fyrsta sinn "for the first time," í fyrsta lagi / í öðru lagi "firstly / secondly."

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