Learn Hardcore Icelandic: Stóllinn er þykkastur.

Because Icelandic doesn’t use separate articles like the; definiteness is marked by adding a suffix. stóll is “chair” (indefinite). To say “the chair,” you add -inn (masculine nominative singular) → stóllinn.

What is þykkastur and how does it relate to þykkur?

þykkastur is the superlative form of the adjective þykkur (“thick”). Just like English has “thick,” “thicker,” “thickest,” Icelandic has þykkur, þykkari, þykkastur.

Why does the superlative end in -astur instead of something like -asti?

Adjectives ending in -ur form the masculine nominative singular superlative by replacing -ur with -astur. So you take þykkur, drop -ur, add -astur → þykkastur.

How do you form the superlative for feminine and neuter nouns?

You use different endings so the adjective agrees in gender, number, and case: • Feminine nominative singular: -asta
(e.g. bókin er þykkasta – “the book is thickest”)
• Neuter nominative singular: -ast
(e.g. borðið er þykkast – “the table is thickest”)

Do I always need to use a definite noun with a superlative adjective?

Yes. In Icelandic, superlatives must go with definite nouns. That’s why you see stóllinn (definite) + þykkastur (superlative).

How would I say “The chair is the thickest of all”?

Add the prepositional phrase af öllum (“of all”):
Stóllinn er þykkastur af öllum.

What is the comparative of þykkur, and how do I use it?

The comparative is formed with -ari on adjectives ending in -ur:
þykkur → þykkari (“thicker”).
Example: Stóllinn er þykkari en bekkurinn.
(“The chair is thicker than the bench.”)

How do I pronounce þykkastur?

Break it down:
• þ = voiceless “th” like in think
• y = close front rounded vowel (like German ü)
• kk = hard /k/ sound
• a = /a/ as in father
• stur = /stur/ with clear /s/ and /t/
Approximation: THÜK-kas-tur (stress on the first syllable).