Maðurinn er ríkur.

Because -inn is the definite article attached to the noun.

• maður = man
• maðurinn = the man

Unlike English, Icelandic usually puts the at the end of the noun instead of using a separate word.

So in this sentence:

• Maðurinn = the man

-inn is the masculine singular form of the attached definite article in the nominative.

In other words, it is the Icelandic way of saying the here.

With this noun:

• maður = man
• maðurinn = the man

You do not say a separate word for the in this sentence.

Er is the present singular form of the verb vera (to be).

So:

• vera = to be
• er = is

In Maðurinn er ríkur, er corresponds to English is.

Because ríkur is an adjective that must agree with the noun it describes.

Here it refers to maðurinn, which is:

• masculine
• singular
• nominative

So the adjective also appears in the masculine singular nominative form:

• masculine: ríkur
• feminine: rík
• neuter: ríkt

Since maðurinn is masculine singular, ríkur is the correct form.

Because here ríkur is not directly placed before the noun as in a rich man. Instead, it is a predicate adjective, linked to the subject by the verb er.

So the structure is:

• Maðurinn = subject
• er = is
• ríkur = rich

This is the same basic pattern as English The man is rich.

If you wanted a rich man, that would be a different structure, for example ríkur maður.

Yes. The subject maðurinn is nominative, and after the verb vera (to be), the predicate adjective usually matches the subject in case, gender, and number.

So:

• maðurinn = nominative masculine singular
• ríkur = nominative masculine singular

That agreement is an important feature of Icelandic grammar.

The dictionary forms are:

• maðurinn → maður (man)
• er → vera (to be)
• ríkur → ríkur (rich)

This is useful because Icelandic words change form a lot, especially nouns and adjectives.

A rough English-friendly guide is:

• Maðurinn ≈ MAH-thur-rin
• er ≈ ehr
• ríkur ≈ REE-kur

A few notes:

• ð in Maðurinn is like the th in this
• á is pronounced like ow in now
• r is typically trilled or tapped
• í is a long ee sound

This is only an approximation, but it helps get started.

You add ekki (not):

• Maðurinn er ekki ríkur. = The man is not rich.

So ekki usually comes after the verb er in a simple sentence like this.

You usually switch the verb and the subject:

• Er maðurinn ríkur? = Is the man rich?

This is very similar to English word order in yes/no questions.

Statement:

• Maðurinn er ríkur.

Question:

• Er maðurinn ríkur?

It is possible to change word order in Icelandic for emphasis or style, but Maðurinn er ríkur is the normal, neutral way to say it.

Ríkur er maðurinn sounds marked or literary, something like emphasizing rich.

So as a learner, the safest basic pattern is:

• Subject + verb + adjective
• Maðurinn er ríkur

Usually, the definite article is attached to the noun, as in maðurinn.

Icelandic can also use a separate demonstrative-like word in some contexts, but for a basic sentence like this, the normal form is the attached article:

• maðurinn = the man

So for everyday beginner use, think of -inn as the usual way of saying the here.

Yes. The adjective changes to match the noun.

For example:

• Maðurinn er ríkur. = masculine singular
• Konan er rík. = feminine singular
• Barnið er ríkt. = neuter singular

So one important Icelandic habit is: adjectives must agree with the noun in gender, number, and often case.