Learn Hardcore Icelandic: Jakkinn minn er þykkastur í flugvélinni. - My jacket is the thickest in the airplane.

In Icelandic, a noun with a possessive pronoun usually takes the definite ending and then the pronoun follows. You start with jakki (“a jacket”), add the masculine definite suffix -inn → jakkinn (“the jacket”), and then attach minn (“my”). Hence jakkinn minn = “the jacket of mine” = “my jacket.” Swapping the order (minn jakki) or dropping the suffix (jakki minn) sounds non-idiomatic here.

How do we form the comparative and superlative of þykkur (“thick”)?

Icelandic adjectives typically go:
• Positive: þykkur (“thick”)
• Comparative: þykkari (“thicker”)
• Superlative: þykkastur (“thickest”)

In our sentence Jakkinn minn er þykkastur, you’re using the superlative to say “my jacket is the thickest.”

Why is the superlative þykkastur ending in -stur instead of something like -sti?

Most Icelandic superlatives are built on the root + -astur, and then you decline that form for gender, number, and case. Here the root þykk- + a + stur gives þykkastur (nominative masculine singular). You do not manufacture a special “-sti” ending.

Why isn’t there a separate definite article before þykkastur? In English we say “the thickest.”

When a superlative appears predicatively (after vera “to be”), Icelandic does not use an additional article. The adjective’s superlative form alone carries the meaning “the thickest.” So Jakkinn minn er þykkastur = “My jacket is the thickest.”

What case is used after í in í flugvélinni, and why?

The preposition í governs the dative when it describes a static location (“where something is”). Hence flugvél (feminine noun) in the definite dative singular becomes flugvélinni, and í flugvélinni means “in the plane.” (If you were going into the plane, motion toward, you’d use the accusative: í flugvélina.)

How is flugvélinni formed? Why the long -inni ending?

flugvél is a feminine 1st-declension noun. Its definite dative singular ending is -inni.
• Indef. nom.sg.: flugvél
• Def. nom.sg.: flugvélin
• Def. dat.sg.: flugvélinni

So í flugvélinni = “in the (air)plane.”

How do you pronounce þykkastur?

The letter þ is like the voiceless “th” in English think. The double kk shows the preceding vowel is short. A rough phonetic rendering is [ˈθɪkːa.stʏr], i.e. “THIK-kass-tur.”

Could you use á flugvélinni instead of í flugvélinni?

Normally í is used for being inside something (“in the plane”). Using á flugvélinni would suggest being “on top of” or “on” the plane’s surface. So stick with í flugvélinni for “in the plane.”

If I want to say “My jacket is the thickest of all the jackets on the plane,” how do I express “of all the jackets”?

You can add an af + dative phrase to show “out of all.” For example:
Jakkinn minn er þykkastur af öllum jökkum í flugvélinni.
Here af öllum jökkum = “out of all jackets.”