kasta ("to throw") looks like the friendliest verb in the world — a plain weak Class-1 verb, kasta / kastaði / kastað, no stem changes. And then it ambushes you twice. First, the u-umlaut: "they threw" is köstuðu, with a → ö. Second, and far more important, kasta takes a DATIVE object. You do not throw a ball; you throw to a ball, structurally. kasta bolta — where bolta is dative — is the single fact that separates someone who has studied this verb from someone who is guessing. English gives no warning at all, because "throw the ball" looks like an ordinary direct object.
Conjugation
Class: weak, Class 1 (the -aði preterite, the tala type). Auxiliary: hafa — ég hef kastað "I have thrown." The stem kast- becomes köst- before any ending containing -u-.
| Principal parts | |
|---|---|
| Infinitive | að kasta |
| 1sg present | kasta |
| 1sg past | kastaði |
| 3pl past | köstuðu |
| Supine | kastað |
| Person | Present (nútíð) | Past (þátíð) |
|---|---|---|
| ég | kasta | kastaði |
| þú | kastar | kastaðir |
| hann / hún / það | kastar | kastaði |
| við | köstum | köstuðum |
| þið | kastið | köstuðuð |
| þeir / þær / þau | kasta | köstuðu |
| Person | Present subjunctive | Past subjunctive |
|---|---|---|
| ég | kasti | kastaði |
| þú | kastir | kastaðir |
| hann / hún / það | kasti | kastaði |
| við | köstum | köstuðum |
| þið | kastið | köstuðuð |
| þeir / þær / þau | kasti | köstuðu |
| Non-finite & imperative | |
|---|---|
| Imperative (þú) | kastaðu! |
| Imperative (þið) | kastið! |
| Supine | kastað |
| Past participle (m/f/n) | kastaður / köstuð / kastað |
| Middle voice (miðmynd) | kastast — "to be thrown / get tossed about" |
The dative object: kasta einhverju
Here is the headline rule, and it is not in any conjugation table: kasta governs the dative. You throw to a thing. kasta bolta "throw a ball" — bolta is the dative of bolti. kasta steini "throw a stone" — steini is the dative of steinn. There is no recovering this from English, where "throw" takes a plain direct object. You simply tag kasta in memory as a dative verb and decline whatever you throw into the dative.
Kastaðu boltanum til mín!
Throw me the ball!
Strákarnir köstuðu snjóboltum hver í annan.
The boys threw snowballs at one another.
Hann kastaði töskunni upp í efstu hilluna.
He threw the bag up onto the top shelf.
In the first example, "the ball" is boltanum — dative singular with the article — not the accusative boltann. This is the form to burn in as your template.
Why dative? A family of verbs
The dative is not random. kasta belongs to a coherent group of verbs of moving something away from a point or causing motion, which in Icelandic naturally take the dative: henda ("throw away, chuck"), ýta ("push"), sparka ("kick"), fleygja ("fling"). Thinking of the thrown object as something sent off from you — propelled away, dative of direction — makes the case feel less arbitrary and lets you predict it across the whole group.
Ekki henda gömlu blöðunum — við endurvinnum þau.
Don't throw out the old papers — we recycle them.
kasta í + accusative — "throw at, throw into"
When you aim at a target or throw something into a place, use kasta + the noun thrown (dative) + í + the target (accusative). The dative of what you throw and the accusative of the target sit side by side — a good drill for keeping the two cases apart.
Krakkarnir köstuðu steinum í gluggann.
The kids threw stones at the window.
Hún kastaði bréfinu í ruslið.
She threw the letter into the bin.
Idioms and the middle voice
kasta anchors several everyday idioms: kasta upp ("throw up, vomit"), kasta kveðju á einhvern ("toss someone a greeting, say a quick hello"), and kasta mæðinni ("catch one's breath"). The middle voice kastast means "to be thrown / get tossed about," as in rough seas.
Báturinn kastaðist til í öldunum.
The boat was tossed about in the waves.
Common Mistakes
❌ Kastaðu boltann til mín.
Incorrect — kasta takes the DATIVE; 'the ball' is boltanum, not the accusative boltann.
✅ Kastaðu boltanum til mín.
Throw me the ball.
❌ Þeir kastaðu snjó í hvor annan.
Incorrect — the 3pl past umlauts: köstuðu, not kastaðu.
✅ Þeir köstuðu snjó í hvorn annan.
They threw snow at each other.
❌ Hann kastaði steininn í vegginn.
Incorrect — the thing thrown is dative (steini); only the target after í is accusative.
✅ Hann kastaði steini í vegginn.
He threw a stone at the wall.
❌ Við köstum boltanum í gær.
Incorrect — köstum is present; the past 'we threw' is köstuðum.
✅ Við köstuðum boltanum í gær.
We threw the ball yesterday.
Key Takeaways
- kasta / kastaði / köstuðu / kastað — a regular weak Class-1 verb with an -aði past.
- u-umlaut: stem a → ö before any -u- ending (köstum, köstuðum, köstuðu, köstuð).
- The headline rule: kasta takes a DATIVE object — kasta bolta, steini, töskunni. English gives no warning.
- kasta í
- accusative = "throw at / into": thrown thing stays dative, target is accusative.
- Same-case family: henda, sparka, ýta, fleygja all take the dative. Middle voice kastast = "be tossed about." Auxiliary is hafa: ég hef kastað.
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Start learning Icelandic→Related Topics
- Verbs and the Case of Their ObjectsB1 — Icelandic verbs assign a fixed case to their object that you cannot predict from meaning: most take the accusative (sjá hann), a sizable cluster take the dative (hjálpa honum), a few take the genitive (sakna hennar), and ditransitives take dative-then-accusative (gefa honum bók) — why object case is lexical, and the high-frequency dative-governing verbs to memorise.
- U-Umlaut as a Sound Alternation (a → ö)A2 — When a u appears (or once appeared) in the next syllable, a stem 'a' is rounded to 'ö' — barn → börn, dagur → dögum, kalla → köllum. This is the living u-umlaut (u-hljóðvarp), an automatic, predictable rounding that explains why so many Icelandic paradigms 'change their vowel'.
- The Weak Preterite: -aði, -di, -ði, -tiA2 — How to choose and form the weak past tense — Class-1 -a verbs take -aði (tala → talaði, plural töluðum), Class-2 verbs take the short dental -di/-ði/-ti picked by the preceding sound (reyndi, dæmdi, keypti) — with the full tala paradigm and the 'when in doubt, -aði' default for unknown verbs.
- Dative-Subject Verbs: mér finnst, mér líkar, mér tekstB1 — The family of Icelandic verbs whose grammatical subject is in the DATIVE — finnast 'think', líka 'like', takast 'manage', leiðast 'be bored', batna 'recover', detta í hug 'occur to', and the vera-kalt/heitt feeling phrases — with the crucial rule that the verb agrees with the nominative THEME, not with the dative experiencer, so it can be plural while 'mér' stays singular.
- gleyma (to forget)A2 — Full conjugation of the weak verb gleyma (gleymi / gleymdi / gleymdu / gleymt), with its crucial DATIVE object (gleyma einhverju), the construction gleyma að + infinitive, and the contrast with muna (remember), which takes the accusative.