Prepositional Idioms and Verb + Preposition

By B2 you know which case each preposition governs in the abstract. The wall you hit next is different: a large set of verbs and adjectives select a specific preposition, and that preposition then drags along its own case — and neither the preposition nor the case is what English would lead you to expect. "Wait for the bus" is not *bíða fyrir strætó but bíða eftir strætó (+ dative). "Look forward to summer" is not *hlakka fram til anything sensible from English but hlakka til sumarsins (+ genitive). These are lexicalised units: the verb comes glued to a preposition, and the preposition's case rides along. You cannot reason them out from meaning, and you cannot transfer them from English. You learn each one as a single chunk: verb + preposition + case. (This page assumes you already know the basic "which preposition takes which case" rules; here the point is that the verb picks the preposition, often against all English intuition.)

Why English intuition fails here

English verbs also select prepositions — "wait for", "rely on", "think about". The trouble is that the Icelandic choice rarely lines up with the English one, and even when the preposition feels familiar, the case is an extra fact you have to store. "Think about something" uses um, which is fine — but um here takes the accusative, and you only know that because hugsa um is stored with its case. "Be in love with someone" uses af (not með "with"!), and af takes the dative. Two independent pieces of unpredictable information per phrase: the preposition, and the case.

bíða eftir + dative — "wait for"

The everyday "wait for" is bíða eftir + dative. English "for" tempts fyrir; the Icelandic preposition is eftir (which on its own often means "after"), and it governs the dative here. This is one of the highest-frequency pairings in the language, and one of the most reliably mis-formed by English speakers.

hlakka til + genitive — "look forward to"

Here is the standout case. "Look forward to" is hlakka til, and til is one of the genitive prepositions — so what you look forward to goes in the genitive: hlakka til sumarsins "look forward to the summer", hlakka til jólanna "look forward to Christmas". This is one of the few productive spots where a genitive-governing preposition shows up inside an everyday verbal idiom, and nothing in English ("look forward to", which feels like a dative-ish goal) predicts the genitive.

A second quirk: hlakka is often used impersonally with an accusative experiencer in careful Icelandic — mig hlakkar til — though ég hlakka til (personal) is extremely common in speech. Either way the til-phrase stays genitive.

hugsa um + accusative — "think about"

"Think about / think of" someone or something is hugsa um, and um here takes the accusative. (Don't confuse it with hugsa sér "imagine".) The accusative is invisible on many nouns but shows up clearly on pronouns: hugsa um *þig* "think about you", not *um þér.

treysta á + accusative — "rely on, trust in"

"Rely on / count on" is treysta á + accusative. (The plain verb treysta + dative means "trust" a person — ég treysti þér "I trust you"; the á-construction shifts the sense to "rely on, depend on".) English "on" happens to match á here, but the accusative is the part you must store, and the two treysta patterns — bare dative vs. á + accusative — are easy to mix up.

taka þátt í + dative — "take part in"

The light-verb idiom taka þátt ("take part") obligatorily attaches í + dative: taka þátt í keppninni "take part in the competition". English "in" matches í, but learners constantly drop the preposition (*taka þátt keppninni) — and the case is dative, not the accusative í takes in its motion sense.

spyrja um + accusative — "ask about"

"Ask about" something is spyrja um + accusative: spyrja um veginn "ask about the road / for directions". (Be careful: spyrja takes its person asked in the accusative too — spyrja mig "ask me" — so spyrja mig um veðrið is "ask me about the weather", two accusatives.)

Adjective + preposition: hrifinn af, ástfanginn af

Adjectives select prepositions and cases too, and two emotional ones share a surprising choice: af + dative where English uses "of" or "with".

• vera hrifinn af
  • dative — "be fond of, be taken with, like" (hrifinn agrees: hrifin fem., hrifið neut.)
• vera ástfanginn af
  • dative — "be in love with"

The trap in vera ástfanginn af is that English "in love with" points straight at með ("with") — but Icelandic uses af + dative. And because hrifinn and ástfanginn are past-participle adjectives, they agree with their subject in gender and number.

Reference table

The preposition and its case are not optional decoration — they are the phrase. Memorise the whole row.

English vs Icelandic

The deep point is that the verb is a lock and the preposition is its key — and the key is rarely the English one. "Wait for" → eftir (not fyrir), "be in love with" → af (not með), "look forward to" → til (and with the genitive). Even where the preposition coincides — um for "about", á for "on", í for "in" — the case is a second, independent fact you must store. There is no shortcut and no logic to extract: these are memorised pairings, and the only safe habit is to learn the verb together with its preposition and case, never the verb alone.

Common Mistakes

Translating English "for" as fyrir is the classic slip. The verb selects eftir.

Even with the right preposition, the case betrays a half-learned phrase. til is genitive.

English "with" does not become með here. The adjective selects af.

Watch the two treysta patterns: bare treysta + dative ("trust someone"), treysta á + accusative ("rely on").

Key Takeaways

• Many verbs and adjectives select a fixed preposition, and that preposition drags along its own case — both unpredictable from English.
• Headline pairings: bíða eftir
  • dative ("wait for", not fyrir), hlakka til
    • genitive ("look forward to"), vera ástfanginn af
      • dative ("be in love with", not með).
• Others: hugsa um (acc.) "think about", treysta á (acc.) "rely on", taka þátt í (dat.) "take part in", spyrja um (acc.) "ask about", vera hrifinn af (dat.) "be fond of".
• Even a familiar-looking preposition carries an independent case fact you must store (um
  • accusative, í
    • dative here).
• Learn each as one unit — verb + preposition + case — never the verb on its own.