The Dative Singular -i and When It Appears

The dative singular of strong masculine and neuter nouns has a small, troublesome ending all of its own: an unstressed -i. Hestur ("horse") has dative hesti; land ("land, country") has dative landi; hús ("house") has dative húsi; barn ("child") has dative barni. But not every noun takes it, a few classes go bare for lexical reasons, and — the point learners most often get wrong — a thick layer of everyday phrases (í dag "today," á morgun "tomorrow," bera á borð "to serve") looks like a stripped-down dative but is actually in the accusative, where there is no -i to begin with. The result is a genuinely lexicalised corner of the grammar that English speakers under-mark — they treat the dative like the accusative and drop the -i. This page is only about when the -i appears; for what the dative does (governed by prepositions and verbs), see the two-case and preposition pages.

What the dative -i is

Across most strong masculine and neuter nouns, the dative singular is formed by adding -i to the stem. It is unstressed and never accented — even on a noun whose stem carries an accented vowel, the dative ending is a plain short i (á húsi, not \á húsí*). Here is the ending in its home environment, the basic strong paradigms:

The key observation for a learner is structural. In the neuter, the nominative and accusative are identical (land, land), and so is the genitive's job easy to see — but the dative is the one singular case with a visible ending of its own. So if you never add the -i, your neuter dative looks exactly like the nominative/accusative, and the sentence loses the very signal that marks it as dative. That is the most common English-speaker error on this page, and it comes from the fact that English has no case endings at all to copy.

Nouns that reliably keep the -i

The productive, default situation is that a strong masculine or neuter noun takes -i in the dative singular. When you form a fresh dative — a new indirect object, a noun under a preposition you are reasoning about live — the safe move is to add -i. This is true of the overwhelming majority of these nouns:

Notice borð → borði in the productive paradigm — bókin liggur á borðinu ("the book is on the table") — even though, as we'll see, the same noun goes bare in the frozen idiom bera á borð ("to serve"). When you are building a dative live, the -i is the rule.

Two reasons you'll see no -i: bare-dative noun classes, and accusative fixed phrases

There are two quite different reasons a noun surfaces without the dative -i, and the second is where learners go wrong — so keep them apart.

First, some noun classes simply don't take the dative ending. Most masculines and neuters whose stem already ends in a vowel, or certain monosyllables and loanwords, have a genuinely bare dative. A masculine like skór ("shoe") has dative skó (vowel stem, no added -i); many neuter loanwords (kort "card/map," sjampó "shampoo") stay bare. These are lexical facts about the word, not optional style.

Second — and this is the bigger trap — a great many everyday phrases are not in the dative at all; they are in the ACCUSATIVE, where strong masculines and neuters never had an -i to begin with. í dag, á morgun, and bera á borð all use í/á in their motion-or-time sense, which governs the accusative (just like í veitingahúsið "into the restaurant"). So dag is the accusative of dagur, morgun the accusative of morgunn, borð the accusative of borð — they look like a "stripped" dative, but the missing -i is simply the accusative doing its normal job:

So the same noun borð gives you accusative bera á borð ("to serve," motion onto the table) and dative á borðinu ("on the table," static location) — the case alternation, not a "frozen dative," is doing the work. Likewise dagur ("day") has a perfectly normal dative degi (á þeim degi "on that day"), but í dag ("today") is the time-accusative dag. You do not reason these out under the dative rule; you store í dag, á morgun, bera á borð whole, and remember they are not datives.

The doublet: formal -i vs colloquial bare

A smaller, more interesting group of nouns shows a doublet: the -i is optional, and the choice carries a register signal. Formal and written Icelandic favours the fuller form with -i; relaxed speech often drops it. The clearest everyday case is the masculine hlutur / phrases around it, and several time and place nouns where you will hear both. The historically "correct" written form keeps the ending; the spoken form is freer.

A textbook example is the noun friður ("peace"): the older, more formal dative is friði (í friði "in peace" is still universal), but you also meet bare stems in some fixed religious or elevated phrases (í Guðs friði). More productively, in careful writing you will see the -i retained where casual speech might let it slip. The honest summary: where a doublet exists, the -i form is the safer, more formal choice, and you will never be marked wrong for including it in a productive dative.

There is no clean rule that tells you which nouns allow the doublet — it is partly lexicalised and partly a matter of register. The practical strategy is: in a productive dative, supply the -i; in a set phrase, learn the phrase as given. That covers almost every case correctly.

Why English speakers under-mark this

English has no productive case morphology — the dative "to the horse" is marked by word order and the preposition to, with the noun horse never changing shape. So when an English speaker reaches for the Icelandic dative, the instinct is to leave the noun alone, which produces a bare stem that looks like the accusative. In the neuter especially, where nominative = accusative already (hús, hús), dropping the -i erases the only morphological signal that the noun is in the dative at all. The mirror-image error is over-supplying the -i inside an accusative time phrase — saying \í degi for "today" instead of í dag — because the learner has correctly learned "datives take -i" and then misapplies it to a phrase that is actually accusative. The discipline, then, is twofold: add -i when you are building a live dative (static location, *með, an indirect object), and leave the accusative time/motion phrases exactly as you learned them.

Common Mistakes

Key Takeaways

• Strong masculine and neuter nouns take an unstressed -i in the dative singular (hesti, landi, húsi, barni) — and it never carries an accent.
• In the neuter, the dative is the only singular case with its own ending, so dropping the -i makes the dative look like the nominative/accusative — the commonest English-speaker error.
• A few classes go bare for lexical reasons (vowel stems like skó, some loanwords). But the phrases learners stumble on — í dag, á morgun, bera á borð — are not bare datives at all; they are accusatives (motion/time í/á), so the -i never belonged there. Learn them as units.
• The same noun can show both cases: accusative bera á borð ("to serve," motion onto) vs dative á borðinu ("on the table," static).
• Where a doublet exists, the -i form is the more formal, safer choice. Rule of thumb: supply -i in a live dative; leave set phrases as given.