Forming abstract nouns (-ni, -leiki, -i)

The Masculine Suffix -leiki

Icelandic frequently derives abstract nouns from adjectives to describe physical properties or personal traits. A common suffix for this is -leiki. Nouns ending in -leiki (like harðleiki for hardness, or sterkleiki for strength) are weak masculine nouns.

Because these are weak masculine nouns ending in -i, their accusative, dative, and genitive forms all end in -a.

The Feminine Suffix -ni

Another common suffix is -ni. Nouns formed this way, such as viðkvæmni (fragility) or nákvæmni (precision), are always feminine.

This suffix is especially common for behavioral traits derived from adjectives ending in -inn, such as hlýðinn (obedient) becoming hlýðni (obedience), and feiminn (shy) becoming feimni.

The Masculine Suffix -leikur

Sometimes, the masculine suffix takes the strong form -leikur instead of the weak -leiki. Because they end in a consonant, they follow strong declension patterns. For example, sætur (sweet) becomes sætleikur.

The Neuter Suffix -i

Finally, some adjectives form neuter abstract nouns by adding the suffix -i. Words like mikilvægi (importance), erfiði (hardship), and gegnsæi (transparency) belong to this group.

Since they are neuter nouns ending in a vowel, their core forms are extremely stable and do not change endings in the accusative or dative cases.

Let's look at one final example combining a weak masculine noun in the accusative case (harðleika) with a neuter noun that stays exactly the same (gegnsæi).