Ordinals in Dates, Sequences, and Royalty

You already know how the ordinals are built — fyrsti, annar, þriðji, fjórði, fimmti … and that they decline like weak adjectives. This page is about putting them to work. Ordinals do an enormous amount of everyday labour in Icelandic: they carry every date, every floor of a building, every "for the first time," and the number of every king and pope. The single insight that ties all these uses together is that a written numeral or a regnal letter usually hides a fully declined ordinal. A 3. in a date is not "three" — it is þriðja, declined to agree with its context; a X after a king's name is not "ten" — it is tíundi, the ordinal. Read these aloud wrong and you sound like a tourist; read the hidden ordinal correctly and you sound like a native. (Ordinal formation lives on numbers/ordinals; dates in general on numbers/dates-and-time; here we focus on use.)

Dates: the period is a declined ordinal

Icelandic dates are ordinals all the way down. Þriðji mars is "the third of March," literally "third March," with þriðji agreeing with the unspoken masculine noun dagur "day." When you write the date in digits, the period after the numeral is the ordinal — 3. mars is read aloud as þriðji mars, never as the cardinal þrír. The dot is doing the work of a whole ordinal word, and that word is declined.

The catch that trips up English speakers is the declension. In the bare statement "today is the third," the ordinal is nominative — þriðji. But the moment the date appears after a preposition or in an oblique slot, the ordinal changes ending to match. With þann (accusative), the date goes accusative: þann þriðja mars. So the very same written 3. is read þriðji in one sentence and þriðja in another, depending on the case the grammar demands.

Floors: á annarri hæð, á þriðju hæð

Buildings are counted with ordinals, and because hæð "floor, storey" is feminine, the ordinal must take its weak feminine ending — which is -u in the oblique cases after the preposition á "on." So "on the third floor" is á þriðju hæð, not á þriðja hæð; the þriðju is feminine, agreeing with hæð. This is a place where the gender of the noun reaches back and reshapes the ordinal.

One vocabulary note worth banking: the street-level floor is normally called the jarðhæð "ground floor," and the numbered floors (fyrsta hæð, önnur hæð, þriðja hæð …) climb up from there. So jarðhæð is the entrance level and önnur hæð is two floors of stairs above it. The grammar is the same whichever counting convention a given building uses: hæð is feminine, so the ordinal always takes its weak feminine ending — á annarri hæð, á þriðju hæð, á fjórðu hæð.

Sequence phrases: í fyrsta sinn, í annað sinn

Ordinals power a family of fixed expressions about order and repetition, most built on the neuter noun sinn "time, occasion." Í fyrsta sinn is "for the first time"; í annað sinn is "for the second time"; í þriðja sinn, "for the third time." Because sinn is neuter and the phrase is in the accusative (after í with motion-through-time sense), the ordinal takes the neuter ending — and here is where annar shows its irregular face: the neuter is annað, never *annari or \öðru* in this slot.

The same ordinals also enumerate points in an argument: í fyrsta lagi … í öðru lagi … í þriðja lagi "firstly … secondly … thirdly," using the neuter noun lag in the dative. Note öðru — the neuter dative of annar — which catches everyone the first time.

Royalty and popes: Kristján tíundi

When a king, queen or pope bears a number, Icelandic uses the ordinal, placed after the name and treated as a weak adjective agreeing with it — just like English Christian the Tenth but without the the. The Roman numeral you see in writing (Kristján X) is read as the spoken ordinal tíundi, declined to match the name's case in the sentence.

Because the regnal ordinal is a weak adjective, it declines with the name: um Kristján tíunda "about Christian X" (accusative tíunda), til Kristjáns tíunda "of Christian X" (genitive). The Roman X on the page hides not just an ordinal but a case-marked one. This is exactly parallel to the date situation: a compact written symbol (X, 3.) stands in for a fully inflected ordinal word.

The thread: written symbols hide declined ordinals

Everything on this page is one habit of the language: a terse written form — a numeral with a period, a Roman numeral after a name — is a shorthand for a fully declined weak ordinal. 3. = þriðji (or þriðja, or þriðju, depending on context); X = tíundi (or tíunda); a floor number bends to the feminine hæð; a date bends to whatever case the preposition assigns. The reader is expected to reinflate the symbol into the correct ordinal form on the fly. English has nothing like this: our 3rd and X are frozen, caseless tags. So the skill to build is reading the hidden ordinal out in the case the sentence demands — and that skill rests entirely on knowing the weak ordinal declension. (For fractions, where ordinals reappear — þriðjungur "a third," fjórðungur "a quarter" — see numbers/fractions-and-arithmetic.)

Common Mistakes

Dates are ordinals. The cardinal fimm "five" is wrong here; the date is fimmti "fifth," which is what the written 5. stands for.

The dot after the digit is the ordinal marker. Reading 3. as þrír is the classic learner slip; read it as þriðji, declined to the sentence.

Floors are feminine (hæð), so the ordinal goes feminine: þriðju, annarri, fjórðu — not the -a forms.

A king's number is an ordinal, exactly as English says the Tenth, not Ten. The Roman X is read tíundi, declined with the name.

Key Takeaways

• Dates are ordinals:
  3. mars
  = þriðji mars, and the written period is the ordinal. After þann it goes accusative — þann þriðja mars — so read the hidden ordinal in the case the sentence demands.
• Floors use ordinals agreeing with feminine hæð → weak feminine: á þriðju hæð, á annarri hæð, á fjórðu hæð. (And fyrsta hæð is the ground floor.)
• Sequence phrases: í fyrsta sinn "for the first time," í annað sinn (neuter annað), í fyrsta lagi / í öðru lagi "firstly / secondly" (neuter dative öðru).
• Royalty and popes take the ordinal after the name, declining with it: Kristján tíundi, um Kristján tíunda, Margrét önnur.
• The unifying rule: a written 3. or regnal X is shorthand for a fully declined weak ordinal — reinflate it correctly when you read aloud.