Icelandic adjectives must change their endings to match the nouns they describe.

This matching process is known as declension.

You’ll need to pay close attention to both the gender and the number of the noun.

Icelandic has three grammatical genders: masculine, feminine, and neuter.

Nouns can also be either singular or plural.

When you use an adjective, its ending has to reflect these two important details.

Icelandic grammar is highly standardized across the entire country.

You don’t need to worry about regional dialects changing these adjective endings.

Whether you’re in Reykjavík or Akureyri, these rules remain exactly the same.

Why Icelandic adjectives change

In English, adjectives stay the exact same regardless of what they describe.

We say “a good boy”, “a good girl”, and “good houses”.

The word “good” never changes its shape.

In Icelandic, adjectives are required to agree with the noun.

If the noun is masculine, the adjective must take a masculine form.

If you’re talking about multiple items, the adjective must switch to a plural form.

This grammatical agreement helps make Icelandic sentences clear and precise.

The three grammatical genders

Every noun in Icelandic belongs to one of three grammatical genders.

These genders are masculine, feminine, and neuter.

You must memorize the gender of a noun when you first learn it.

The adjective you choose will change its ending based on this gender.

Let’s look at the Icelandic adjective for “yellow”, which is gulur.

If you describe a masculine noun, you use the masculine form gulur.

If you describe a feminine noun, you drop the ending to use the feminine form gul.

If you describe a neuter noun, you add a “t” to use the neuter form gult.

Singular versus plural adjectives

Number simply refers to how many things you’re talking about.

Singular means there’s only one item.

Plural means there’s more than one item.

When a noun becomes plural, the adjective describing it must also become plural.

The plural endings are different for each of the three genders.

For the masculine plural of “yellow”, you say gulir.

For the feminine plural, you say gular.

For the neuter plural, you simply say gul.

Basic adjective declension table

To see this clearly, let’s look at the common adjective góður (good).

The table below shows how this adjective declines in the basic nominative case.

It covers all three genders in both singular and plural forms.

As you learn more Icelandic, you’ll also learn how these adjectives change based on grammatical cases.

For beginners, mastering this basic gender and number agreement is the most important first step.

Adjectives in real sentences

Seeing these adjectives in context will help you understand how they work.

Here’s an example using a masculine singular noun (strákur).

Here’s an example using a feminine singular noun (stelpa).

Here’s an example using a neuter singular noun (barn).

Now let’s look at how the plural forms work in real sentences.

Here’s an example using a masculine plural noun (hestar).

Here’s an example using a feminine plural noun (bækur).

Here’s an example using a neuter plural noun (hús).

Practice replacing the nouns in these sentences with other words you know.

Make sure you always match the adjective to the noun’s specific gender and number.