Mosinn er blautur eftir rigninguna.

The base form is mosi, which means moss.

The ending -inn is the suffixed definite article, so:

• mosi = moss
• mosinn = the moss

Icelandic usually adds the to the end of the noun instead of using a separate word the way English does.

Mosinn is in the nominative singular.

It is the subject of the sentence, and subjects are normally in the nominative in Icelandic.

So the structure is:

• Mosinn = the subject
• er = is
• blautur = wet

Er is the present singular form of the verb vera, which means to be.

So:

• ég er = I am
• þú ert = you are
• hann/hún/það er = he/she/it is

Since mosinn is singular, the verb is er.

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

Mosi is a masculine singular noun, and here it is nominative, so the adjective also appears in the masculine singular nominative form:

• masculine: blautur
• feminine: blaut
• neuter: blautt

So mosinn er blautur means the moss is wet.

This is a very common question.

After er, the adjective is a predicate adjective, and Icelandic normally uses the strong form there:

• Mosinn er blautur. = The moss is wet.

But when the adjective comes before a definite noun, Icelandic often uses the weak form:

• blauti mosinn = the wet moss

So:

• mosinn er blautur = predicate adjective
• blauti mosinn = adjective directly modifying a definite noun

That is why blautur is correct here.

Here eftir means after in a time sense:

• eftir rigninguna = after the rain

So the sentence says the moss is wet after the rain.

Be aware that eftir can have other meanings in other contexts, but after is the right one here.

The base noun is rigning, a feminine noun meaning rain or rainfall.

In this sentence, rigninguna is:

• singular
• definite = the rain
• accusative

So:

• rigning = rain
• rigninguna = the rain (accusative form)

The accusative is used here because the preposition eftir takes the accusative in this time meaning.

Because Icelandic changes noun endings for both case and definiteness.

With rigning, you are not just adding the. You are also putting the word into the form required by the preposition eftir.

That is why English speakers often feel that Icelandic definite forms are doing two jobs at once:

1. marking the
2. marking the grammatical case

So rigninguna is not just rigning + the in a simple way; it is the full declined definite form.

Because Icelandic usually uses a suffixed definite article.

Instead of a separate word, the is attached to the noun:

• mosinn = the moss
• rigninguna = the rain

English says the moss and the rain with a separate word. Icelandic usually builds that meaning into the noun itself.

Yes, a little.

The neutral, straightforward order is:

• Mosinn er blautur eftir rigninguna.

But Icelandic can move parts around, especially to emphasize time or place. For example:

• Eftir rigninguna er mosinn blautur. = After the rain, the moss is wet.

That version is also correct. It just puts more focus on after the rain.

Then you would remove the definite article from rigninguna.

A natural form would be:

• eftir rigningu = after rain / after rainfall

So compare:

• eftir rigninguna = after the rain
• eftir rigningu = after rain

That same definite/indefinite difference also applies to mosi / mosinn.

Yes. It is a very typical pattern:

• subject + vera + adjective + adverbial phrase

Here that gives:

• Mosinn = subject
• er = verb
• blautur = predicate adjective
• eftir rigninguna = time phrase

So this sentence is a good model for many other simple Icelandic sentences, such as:

• Jörðin er blaut eftir rigninguna. = The ground is wet after the rain.
• Vegurinn er hálfur eftir snjóinn. = The road is slippery after the snow.