Uppskeran er mikil.

Because Icelandic usually puts the definite article on the end of the noun instead of using a separate word like English the.

• uppskera = harvest
• uppskeran = the harvest

So -an here is part of the definite form of the noun.

The dictionary form is uppskera.

That is the indefinite nominative singular form, the form you would normally look up in a dictionary. It is a feminine noun.

Because Icelandic adjectives must agree with the noun they describe in gender, number, and case.

Here:

• uppskeran is feminine
• singular
• nominative (because it is the subject)

So the adjective must also be feminine singular nominative:

• masculine: mikill
• feminine: mikil
• neuter: mikið

That is why the sentence uses mikil.

The base form is mikill, which is the dictionary form of the adjective.

It is an irregular high-frequency adjective, and some common forms are:

• mikill = masculine singular nominative
• mikil = feminine singular nominative
• mikið = neuter singular nominative/accusative

In this sentence, mikil is the form that matches uppskeran.

This is a very good question. In Uppskeran er mikil, mikil is a predicate adjective because it comes after er (is).

Predicate adjectives in Icelandic agree with the subject in gender, number, and case, but they are not used the same way as adjectives placed directly before a noun.

So:

• uppskeran er mikil = the harvest is large / abundant

Here mikil is simply the correct feminine singular nominative form after er.

It is nominative singular.

You can tell because it is the subject of the sentence, and subjects are normally in the nominative in Icelandic.

So the structure is:

• uppskeran = subject
• er = verb
• mikil = predicate adjective

Because the subject is nominative, the adjective also appears in the nominative.

Yes. This is the basic and most neutral Icelandic word order:

• Subject + Verb + Complement
• Uppskeran + er + mikil

So in that sense, it works very much like English The harvest is abundant.

It depends on context, but with uppskera it usually means something like:

• large
• great
• abundant
• plentiful

So while the literal core idea is big/great, the most natural English meaning with harvest is often abundant or plentiful.

Yes, but it changes the meaning.

• Uppskeran er mikil = the harvest is abundant
• Uppskera er mikil = harvest is abundant or a harvest is abundant, depending on context

The version with -an is definite and refers to a specific harvest. Without it, the noun is indefinite or more general.

A rough English-friendly approximation is:

UHP-skeh-ran er MIH-kil

A few useful notes:

• u in Icelandic is not exactly the English oo
• sk before front vowels can sound different from English sk
• r is usually rolled or tapped
• the i in mikil is short

The exact native pronunciation is worth hearing from audio, but that approximation is enough to get started.