Adjective Declensions

Adjective endings are not completely regular in Icelandic. They depend on the ending of the base of the word to a degree. Other parts of the word may also change in some cases. A sound change may happen to vowels. This is what is called „hljóðvarp“ in Icelandic. It is the same concept as the Umlaut in German. Adjective declinations for case, gender and number are still regular enough that one should be able to get a fair understanding of their patterns with some practice.

Let's look at the adjective for new

Without an article

	Masculine	Feminine	Neuter
Nominative	nýr	ný	nýtt
Accusative	nýjan	nýja	nýtt
Dative	nýjum	nýrri	nýju
Genitive	nýs	nýrrar	nýs

	Plural masculine	Plural feminine	Plurar neuter
Nominative	nýir	nýjar	ný
Accusative	nýja	nýjar	ný
Dative	nýjum	nýjum	nýjum
Genetive	nýrra	nýrra	nýrra

With the definite article

	Masculine	Feminine	Neuter	Plural
Nominative	nýi	nýja	nýja	nýju
Accusative	nýja	nýju	nýja	nýju
Dative	nýja	nýju	nýja	nýju
Genitive	nýja	nýju	nýja	nýju

Here is another example of an adjective, fast, which does in some cases have „hljóðvarp“ (vowel changes)

	Masculine	Feminine	Neuter
Nominative	hraður	hröð	hratt
Accusative	hraðan	hraða	hratt
Dative	hröðum	hraðri	hröðu
Genitive	hraðs	hraðrar	hraðs

	Plural masculine	Plural feminine	Plurar neuter
Nominative	hraðir	hraðar	hröð
Accusative	hraða	hraðar	hröð
Dative	hröðum	hröðum	hröðum
Genetive	hraðra	hraðra	hraðra

With the definite article

	Masculine	Feminine	Neuter	Plural
Nominative	hraði	hraða	hraða	hröðu
Accusative	hraða	hröðu	hraða	hröðu
Dative	hraða	hröðu	hraða	hröðu
Genitive	hraða	hröðu	hraða	hröðu

Now let's look at the adjective for strong. Note how it is declined in mostly the same way as new, but there is only one -t at the end in neuter, nominative, singular and how in genetive, plural there is only one r for strong, but two for new.

	Masculine	Feminine	Neuter
Nominative	sterkur	sterk	sterkt
Accusative	sterkan	sterka	sterkt
Dative	sterkum	sterkrar	sterks
Genitive	sterks	sterkrar	sterks

	Plural masculine	Plural feminine	Plurar neuter
Nominative	sterkir	sterkar	sterk
Accusative	sterka	sterkar	sterk
Dative	sterkum	sterkum	sterkum
Genetive	sterkra	sterkra	sterkra

With the definite article

	Masculine	Feminine	Neuter	Plural
Nominative	sterki	sterka	sterka	sterku
Accusative	sterka	sterku	sterka	sterku
Dative	sterka	sterku	sterka	sterku
Genitive	sterka	sterku	sterka	sterku