Schrijf je adres en postcode duidelijk op de envelop.

Schrijf is the imperative form of schrijven (to write).

In Dutch, the imperative is often just the verb stem:

• schrijven → schrijf
• lopen → loop
• kijken → kijk

So Schrijf je adres en postcode duidelijk op de envelop is a command or instruction: Write your address and postcode clearly on the envelope.

Dutch often uses this bare imperative in instructions, notices, manuals, and forms.

In Dutch, just like in English, commands usually leave out the subject.

Compare:

• English: Write your address clearly.
• Dutch: Schrijf je adres duidelijk.

The subject is understood. In this sentence, it is basically you.

If you want to make it explicit and polite, Dutch often uses u:

• Schrijft u uw adres en postcode duidelijk op de envelop.

So the original sentence is a normal instruction with the subject omitted.

Here, je means your.

That can confuse English speakers because je can also mean you in other contexts.

In this sentence:

• je adres = your address
• je postcode = your postcode

You can tell it means your because it comes directly before a noun.

Compare:

• Je schrijft. = You write.
• Je adres = Your address

So here je is a possessive determiner.

Both can mean your, but they are used differently.

• je = normal, unstressed your
• jouw = stressed or contrastive your

In most ordinary sentences, Dutch prefers je:

• Schrijf je adres op. = normal

You use jouw when you want emphasis or contrast:

• Schrijf jouw adres op, niet mijn adres.
• Is dit jouw postcode?

So in the sentence you gave, je is the natural choice because there is no special emphasis.

Because the possessive je already does that job.

In Dutch, as in English, you normally do not use an article together with a possessive:

• je adres = your address
• not je het adres

Also, one possessive can cover both nouns:

• je adres en postcode

That means your address and postcode.

You do not need to repeat je before both nouns, although you could in some contexts for emphasis:

• je adres en je postcode

But the version with one je is completely normal.

Here duidelijk means something like clearly or legibly.

In context, it means the address and postcode should be easy to read.

So the idea is not just write it, but write it clearly enough that it can be read without difficulty.

A few related words:

• duidelijk = clear / clearly
• leesbaar = readable / legible
• onduidelijk = unclear / unclearly

In practical instructions like this, duidelijk often implies write neatly and legibly.

Because Dutch adverbs often come after the object and before a prepositional phrase.

So this structure is very natural:

• Schrijf
  • je adres en postcode
    • duidelijk
      • op de envelop

That said, Dutch word order with adverbs can be somewhat flexible depending on emphasis. For example:

• Schrijf duidelijk je adres en postcode op de envelop.

This also works, but it puts slightly more emphasis on clearly.

The original sentence sounds very natural for an instruction.

In this sentence, op is best understood as the preposition in op de envelop = on the envelope.

So:

• schrijven op de envelop = to write on the envelope

This is different from the separable verb opschrijven, which means to write down.

Compare:

• Schrijf je adres op. = Write down your address.
• Schrijf je adres op de envelop. = Write your address on the envelope.

That distinction is very important. In your sentence, the meaning is about where to write it: on the envelope.

Because envelop is a de-word in Dutch:

• de envelop

So you would say:

• op de envelop
• een envelop
• de witte envelop

A learner may also notice the spelling. In modern Dutch, envelop is the standard common form. You may occasionally see enveloppe, but envelop is the usual spelling.

Yes. The given sentence is a straightforward instruction, but a more formal or polite version could be:

• Schrijft u uw adres en postcode duidelijk op de envelop.
• Wilt u uw adres en postcode duidelijk op de envelop schrijven?

Notice the changes:

• je becomes uw for formal your
• u is used for polite you
• the verb form changes in the Schrijft u... version

So the original sentence is fine for general instructions, while these versions are more explicitly polite.

Yes, a little.

Dutch allows some flexibility, especially with adverbs like duidelijk, but not every order sounds equally natural.

Natural options include:

• Schrijf je adres en postcode duidelijk op de envelop.
• Schrijf duidelijk je adres en postcode op de envelop.
• Schrijf je adres en postcode op de envelop.
  (without duidelijk)

The original version is a very standard, natural instruction. If you move duidelijk, you may slightly change the emphasis, but the meaning stays basically the same.