Adjectives in the dative singular (-um, -ri, -u)

Prepositions like í (in), á (on), hjá (by), and frá (from) take the dative case when expressing a static location or origin.

When a noun is indefinite, its accompanying adjective takes a strong dative ending based on its gender:

GenderDative EndingExample (stór - big)
Masculine-umstórum
Feminine-ristórri
Neuter-ustóru

Masculine (-um)

The dog sits on a high cliff.
Hundurinn situr á háum kletti.
We stand by a high waterfall.
Við stöndum hjá háum fossi.
Does Jón live in a deep valley?
Býr Jón í djúpum dal?

Feminine (-ri)

If the adjective stem ends in l (like lítil), the -ri ending usually assimilates to match it, becoming -li (lítilli).

Here we live on a big island.
Hérna búum við á stórri eyju.
Is your boyfriend from a small island?
Er kærastinn þinn frá lítilli eyju?

Neuter (-u)

We see a bird by a big volcano.
Við sjáum fugl hjá stóru eldfjalli.
My friend stands by a new volcano.
Vinur minn stendur hjá nýju eldfjalli.