Kaffið er allt of kalt.

Kaffi is the indefinite form, meaning coffee in a general sense.

Kaffið is the definite form, meaning the coffee. In Icelandic, the definite article is usually added to the end of the noun as a suffix rather than written as a separate word.

So:

• kaffi = coffee
• kaffið = the coffee

In this sentence, the speaker is talking about a specific coffee, so kaffið is the natural form.

You usually learn Icelandic nouns together with their grammatical gender. Kaffi is a neuter noun.

There are a few clues here:

• the definite form is kaffið, and -ið is a common neuter definite ending
• the adjective is kalt, which is the neuter singular form of cold

One important warning: you cannot always guess gender safely just from the ending of the noun. Even though patterns help, gender is something you often just have to learn with each word.

Er is the present tense of vera, which means to be.

So here:

• er = is

Because kaffið is singular, Icelandic uses singular er, not plural eru.

Here allt of means far too, much too, or way too.

The core word is of, which can mean too before an adjective:

• of kalt = too cold

Adding allt makes it stronger:

• allt of kalt = far too cold

So the phrase is acting as an intensifier.

No. Even though it looks similar, it does not mean English all of in this sentence.

Here it is a set expression meaning far too. So you should understand:

• allt of kalt = far too cold

not:

• all of cold
• all of the coffee

That would be a misunderstanding.

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

The adjective kaldur is the masculine singular form. But kaffi is neuter singular, so the adjective must also be neuter singular:

• kaldur = masculine singular
• köld = feminine singular
• kalt = neuter singular

So:

• kaffið er kalt = the coffee is cold

This same agreement remains when you add allt of.

Because kalt is being used as a predicate adjective, not directly in front of the noun.

In a sentence like this:

• Kaffið er kalt

the noun kaffið already carries the definiteness, and the adjective after er simply agrees with the subject in gender and number. Icelandic does not normally add a separate definite article to the adjective in this kind of structure.

So kaffið er kalt is the normal pattern.

Yes. That is perfectly natural.

The difference is strength:

• Kaffið er of kalt = The coffee is too cold
• Kaffið er allt of kalt = The coffee is far too cold / much too cold

So allt adds emphasis.

No. This is very standard Icelandic word order for a simple main clause:

• Kaffið = subject
• er = verb
• allt of kalt = complement

So the structure is very similar to English:

• The coffee is far too cold

It is a straightforward sentence grammatically.