Icelandic's famous prepositions — í, á, undir — switch between accusative and dative depending on motion versus rest (see prepositions/two-case-motion-location). It is a relief, then, that a group of common prepositions does no switching at all: they take the accusative every single time, whether something is moving or sitting still. The three to know are um ("about / around / during"), gegnum ("through"), and (í) kringum ("around"). By far the most important is um, which is one of the most overworked words in the language — it covers topics, paths, and time spans, and it anchors a long list of fixed expressions. This page is about these always-accusative prepositions. (The two-case motion/location prepositions are covered separately.)
The good news: no case switching to worry about
With í and á you have to ask "is there a change of location?" before you can pick a case. With um, gegnum, and kringum you skip that question entirely. They govern the accusative full stop. So um + bærinn ("the town") is um bæinn whether you are talking about the town, walking through the town, or staying there for the weekend. One case, always.
Við gengum um bæinn í allan dag.
We walked around town all day. (um → accusative bæinn — and it stays accusative no matter the motion)
Sólin skein gegnum gluggann.
The sun shone through the window. (gegnum → accusative gluggann)
Það var girðing í kringum húsið.
There was a fence around the house. (í kringum → accusative húsið)
um, sense 1: the topic — "about"
The most frequent use of um is to introduce a topic — what you are talking, thinking, or reading about. This is where English "about" lines up neatly, and it is the use you will reach for constantly. Crucially, even though "about a topic" feels completely static — nothing is moving — um is still accusative.
Við vorum að tala um veðrið.
We were talking about the weather. (um → accusative veðrið)
Ég var að hugsa um þig.
I was thinking about you. (um → accusative þig)
Hún skrifaði grein um loftslagsbreytingar.
She wrote an article about climate change. (um → accusative loftslagsbreytingar)
Many of the verbs you use most often pair with um to introduce their topic: tala um ("talk about"), hugsa um ("think about / care for"), vita um ("know about"), spyrja um ("ask about"), lesa um ("read about"). It is worth memorising the verb-plus-um as a unit, because English does not always use "about" where Icelandic uses um (and vice versa).
um, sense 2: the path — "around / about a space"
um also describes motion or extent through or around a space — wandering about a town, travelling around a country, spreading throughout a region. Here English might use "around," "about," or "through." Again: accusative, and again, this is true whether you are actively moving or just describing coverage.
Þau ferðuðust um landið í þrjár vikur.
They travelled around the country for three weeks. (um → accusative landið)
Fréttin barst hratt um allan bæinn.
The news spread quickly all over town. (um → accusative allan bæinn)
Notice this is exactly where a two-case preposition would force a choice — and um does not. That is its appeal: for "moving about / spread across a space," um gives you one reliable form.
um, sense 3: the time span — "during / over"
This is the use English speakers most often miss, and it is high-frequency, so slow down here. um marks a time span — a stretch of time during or over which something happens: um helgina ("over the weekend"), um nóttina ("during the night"), um jólin ("over Christmas"), um sumarið ("over the summer"). And, predictably by now, the noun is accusative.
Við ætlum að slaka á um helgina.
We're going to relax over the weekend. (um → accusative helgina, not dative)
Það snjóaði mikið um nóttina.
It snowed a lot during the night. (um → accusative nóttina)
Þau eru alltaf á Íslandi um jólin.
They're always in Iceland over Christmas. (um → accusative jólin)
Ég vinn mest um sumarið.
I work the most over the summer. (um → accusative sumarið)
There is a real insight buried here. For "during a period," Icelandic often has a choice between um + accusative and í + dative, and they are not interchangeable: um carries the sense of "throughout / over the whole span," painting the period as a single stretch the event sits inside, whereas í leans toward "within / inside" a period. Um helgina says "across the weekend as a whole"; you would not reach for í helginni to mean that. So when you mean "over the course of [a weekend / a night / Christmas / the summer]," um + accusative is the default, and forcing í + dative there is a tell-tale learner error.
gegnum and kringum
The other two are narrower and easier. gegnum means "through" — passing in one side and out the other, physically or figuratively. (You will also see the fuller form í gegnum, which is extremely common and means the same thing; both take the accusative.)
Hann gekk gegnum garðinn til að stytta sér leið.
He walked through the park to take a shortcut. (gegnum → accusative garðinn)
Við komumst í gegnum þetta saman.
We'll get through this together. (í gegnum → accusative þetta; figurative)
kringum (very often í kringum) means "around" in the sense of encircling or surrounding something, and also approximating a number or time ("around three o'clock").
Krakkarnir hlupu í kringum húsið.
The kids ran around the house. (í kringum → accusative húsið)
Við hittumst í kringum sjö.
Let's meet around seven. (í kringum → accusative; approximating a time)
How this differs from English — and why "static = accusative" surprises learners
English does not mark case on prepositional objects at all, so the surprise is not the form but the logic: an English speaker's instinct is that accusative should signal motion and dative should signal rest (that is, after all, how í and á behave). With um/gegnum/kringum that instinct fails completely — talandi um veðrið ("talking about the weather") is utterly static yet accusative; um helgina ("over the weekend") is a period of time yet accusative. The fix is to stop reasoning about case for these three prepositions at all. They are not playing the motion/location game; their case is simply fixed. Memorise "um → accusative, always" the way you memorise that a verb governs the dative.
Common Mistakes
❌ Við tölum um veðrinu.
Incorrect — um always takes the accusative, even for the static 'about a topic': veðrið, not dative veðrinu.
✅ Við tölum um veðrið.
We're talking about the weather. (um → accusative veðrið)
Slipping into dative because "about a topic" feels static. um is accusative regardless.
❌ Við slökum á í helginni.
Incorrect for 'over the weekend' — the set expression is um + accusative helgina.
✅ Við slökum á um helgina.
We relax over the weekend. (um → accusative helgina)
Using í + dative for a time span. "Over the weekend / night / summer" wants um + accusative.
❌ Hún skrifaði grein um loftslagsbreytingum.
Incorrect — um governs the accusative, so loftslagsbreytingar (acc.), not the dative -um form.
✅ Hún skrifaði grein um loftslagsbreytingar.
She wrote an article about climate change.
The plural object after um is still accusative — loftslagsbreytingar, not the dative plural.
❌ Sólin skein gegnum glugganum.
Incorrect — gegnum is accusative-only: gluggann, not the dative glugganum.
✅ Sólin skein gegnum gluggann.
The sun shone through the window. (gegnum → accusative gluggann)
Treating gegnum like a two-case preposition. There is no dative option; it is always accusative.
❌ Ég var að hugsa um þér.
Incorrect — um takes the accusative pronoun þig, not the dative þér.
✅ Ég var að hugsa um þig.
I was thinking about you. (um → accusative þig)
Even with pronouns, um is accusative: þig, not þér.
Key Takeaways
- um, gegnum, (í) kringum take the accusative every time — no motion/location decision to make.
- um is extremely polysemous: it marks a topic ("about" — tala um, hugsa um), a path/space ("around / through" — ferðast um landið), and a time span ("over / during" — um helgina, um nóttina).
- For "over / during a whole period," um + accusative is the default (um helgina, um sumarið); don't replace it with í
- dative.
- gegnum / í gegnum = "through"; (í) kringum = "around / encircling" and also "approximately" with times and numbers.
- The English instinct "accusative = motion, dative = rest" does not apply here — these prepositions have a fixed case. Learn it as a lexical fact, like a verb's government.
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Start learning Icelandic→Related Topics
- Prepositions and Case: OverviewA2 — The central fact of Icelandic prepositions: every preposition governs a case — accusative, dative, or genitive — and a famous handful govern TWO cases, accusative for motion and dative for location, with the motion/location alternation being the single highest-value preposition rule in the language.
- Prepositions of TimeB1 — How Icelandic builds time expressions with prepositions and their cases — í (í dag, í gær as frozen phrases; í viku 'for a week'), á (á mánudaginn — accusative with the article), um + acc (um helgina), fyrir + dat ('ago'), eftir + acc ('after / in'), and the frá ... til span — plus the duration-vs-point contrast (í viku 'for a week' vs eftir viku 'in a week's time').
- Time Phrases and Frozen Temporal IdiomsA2 — Telling the time (Klukkan er þrjú, hálf fjögur, korter í/yfir) and the high-frequency frozen time expressions (í dag, í gær, á morgun, um helgina, í gærkvöldi) whose case and preposition are lexicalised — memorise them as units, don't derive them.
- Two-Case Prepositions: Motion vs LocationA2 — The flagship Icelandic preposition rule: the spatial two-case prepositions í, á, undir, yfir, eftir take the accusative for motion / change of location (fara í bæinn) and the dative for static location / rest (vera í bænum) — the same preposition, the same noun, two endings, decided by whether the action changes where the figure is.