All prepositions can have multiple different meanings depending on context (think about being on a table, on a bus and on drugs), but the core meaning of í, á, yfir and undir is this.
í means in or into,
á means on or onto,
yfir means over, and
undir means under.
Í and á are also used to mean to and at a location. For instance, you’d go í skólann (to school) and have a coffee á kaffihúsi (at a café).
The choice between í or á depends entirely on the location; NOT on whether there is movement or not. You would go í skólann and study í skólanum; go á kaffihús and have a coffee á kaffihúsi.
It’s All About Motion
With the accusative case, these words indicate motion toward a location. In all of these examples, the location is in the accusative.
Settu jakkann bara í skápinn> Just put the jacket in the closet.
Settu dúkinn á borðið> Put the tablecloth onto the table.
Hvað segirðu um að hengja myndina yfir hurðina? > What do you say about hanging the photo above the door?
Þegar mamma kemur í heimsókn fleygi ég óhreina þvottinum bara undir rúmið> When mom comes for a visit, I just throw my dirty laundry under the bed.
With the dative case, these words do not indicate motion toward a location. So, something happening or something being at a location, basically. In all of these examples, the location is in the dative.
Ertu búinn að leita að jakkanum í skápnum? > Have you searched for the jacket in the closet?
Dúkurinn á borðinu er rosalega skítugur > The tablecloth on the table is really dirty.
Myndin sem hangir yfir hurðinni…á hún að vera skökk? > The picture that is hanging above the door…is it supposed to be crooked?
Já, móðir, óhreini þvotturinn er undir rúminu. Ég er svín > Yes, mother, the dirty laundry is under the bed. I am a pig.
It’s always good to see some sentences side-by-side, to really see what’s going on. Notice that the case is the only thing in these sentences that separates the two translations. Each sentence pair starts with motion towards, in the accusative, and then in the dative, without motion toward anything.
Jón hjólar í skólann, og fær lof fyrir > Jón rides a bike to school (from his home), and gets praised for it.
Jón hjólar í skólanum, og fær skammir fyrir > Jón rides a bike in school (around the hallways, or inside the classrooms), and gets scolded for it.
Hoppaðu á borðið > Jump onto the table.
Hoppaðu á borðinu > Jump up and down on the table.
Boltinn flaug yfir mig > The ball flew over me (and maybe hit a window behind me or something).
Boltinn flaug yfir mér > The ball flew around over me (it hovered over my head. Maybe it’s a magic ball, I don’t know).
Barnið er að skríða undir borðið > The child is crawling under the table (from being not-under-the-table, to being under-the-table).
Barnið er að skríða undir borðinu > The child is crawling around under the table.
í and á in Phrasal Verbs
As you’ll recall, in phrasal verbs the prepositiondoesn’t contribute to the meaning at all. It also doesn’t contribute to the case assignment. In these example sentences, it’s the phrasal verb as a whole that decides the case, not the preposition.
Að hringja í e-n > to call sb (accusative)
Ertu búin að hringjaí afa þinn? > Have you called your grandfather yet?
Að heyra í e-u > to hear sth (dative)
Viltu tala hærra? Ég heyri ekki í þér > Can you speak up? I can’t hear you.
Ég er við það að gefast upp á því að læra þetta heimskulega tungumál > I’m just about to give up on learning this stupid language.
Motion Versus Non-Motion?
In this article, I’ve been talking about motion towards (accusative) vs. not motion towards (dative). Sometimes this is explained as motionvs. non-motion, but I’ve found that talking about non-motion can be misleading. There can very well be motion involved with the dative structures; it just isn’ttoward whatever you’re talking about.
Here are a couple sentences with the dative, where there clearly is motion - it’s just not toward the location.
Fólk skokkar mjög mikið á Akureyri > People jog a lot in Akureyri (people jog around Akureyri - they don’t jog from Reykjavík or somewhere to Akureyri).
Halldóra á ekki bíl en hún keyrir mikið í vinnunni> Halldóra doesn’t have a car, but she drives a lot at work (maybe Halldóra is a bus driver, or part of her job is running errands in the company car).
Í, á, yfir and undir basically mean in, on, over and under, respectively. Í and á are also used to mean to or at a location.
They can take either the accusative or the dative. With the accusative they indicate motion toward something, and with the dative they don’t indicate motion toward something.
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