Lestu leiðbeiningarnar vandlega áður en þú byrjar að setja skápinn saman.

Lestu is the singular imperative of lesa (to read). In other words, it means Read! when you are speaking to one person.

The dictionary form lesa is the infinitive, equivalent to English to read. Icelandic usually does not use the infinitive for commands.

So:

• lesa = to read
• Lestu! = Read!

If you were speaking to more than one person, you would normally use Lesið!

leiðbeiningarnar means the instructions.

The base noun is leiðbeining (instruction, feminine noun). In the plural, leiðbeiningar means instructions. When Icelandic adds the definite article the onto the end of the word, it becomes leiðbeiningarnar.

So the breakdown is:

• leiðbeining = instruction
• leiðbeiningar = instructions
• leiðbeiningarnar = the instructions

Here it is the direct object of Lestu, so it is in the accusative plural. For this noun, the accusative plural happens to look the same as the nominative plural in the indefinite form, but with the definite ending attached you get -arnar.

vandlega is an adverb, and it means carefully.

It describes how you should read the instructions. In English, we often make adverbs with -ly:

• careful → carefully

Icelandic often does something similar with -lega:

• vandlegur (careful) → vandlega (carefully)

So Lestu leiðbeiningarnar vandlega means Read the instructions carefully.

áður en is a fixed expression meaning before.

It introduces a clause that tells you what happens later:

• áður en þú byrjar = before you start

The two parts are:

• áður = before / earlier
• en = a conjunction here, helping introduce the following clause

You should learn áður en as a set phrase, because it is very commonly used this way.

In a normal finite clause like this, Icelandic usually does include the subject pronoun. Icelandic is not like Spanish or Italian, where subject pronouns are often dropped.

So:

• áður en þú byrjar = before you start

Leaving out þú here would normally sound incomplete or unnatural in standard Icelandic.

English can sometimes switch to a shorter structure like before starting, but this Icelandic sentence uses a full clause instead.

This is normal in Icelandic. After time words and conjunctions like áður en (before), Icelandic often uses the present tense to refer to something that is still in the future.

So áður en þú byrjar literally uses present tense, but it means:

• before you start

This is actually similar to English, where we also usually say:

• before you start not
• before you will start

So the grammar here is very natural in both languages.

After byrja (to begin / start), Icelandic normally uses að + infinitive.

So:

• byrja að = start to
• byrjar að setja = start to put / start putting

Here, að works a lot like English to before an infinitive.

Examples:

• Ég byrja að lesa. = I start to read.
• Þú byrjar að setja skápinn saman. = You start to assemble the cabinet.

The basic noun is skápur (cabinet / cupboard, masculine noun).

In this sentence, it is the direct object of setja, so it has to be in the accusative. Also, it is definite: the cabinet.

That gives these forms:

• skápur = a cabinet (nominative singular)
• skáp = a cabinet (accusative singular)
• skápinn = the cabinet (accusative singular definite)

So skápinn is the correct form because the sentence is talking about assembling the cabinet as the object of the verb.

saman means together, and in this sentence it is part of the expression setja saman.

• setja = put / place
• setja saman = put together / assemble

So setja skápinn saman means put the cabinet together, which in smoother English is usually assemble the cabinet.

This is a very useful pattern in Icelandic. The word saman often adds the idea of pieces coming together into a whole.

It is partly literal and partly just the normal Icelandic way to say assemble.

Literally, it is something like:

• setja = put
• skápinn = the cabinet
• saman = together

So word-for-word, it is put the cabinet together. That is very close to English, so it is easy to understand, but you should also learn setja saman as a common verb phrase meaning assemble.

That is why this sentence sounds exactly like the kind of instruction you would see in a furniture manual.