Die geldigheidsduur is lank.

It follows a very common Afrikaans pattern:

• Die geldigheidsduur = the subject
• is = the linking verb
• lank = the predicate adjective

So the structure is:

Subject + is + adjective

This is very similar to English The validity period is long.

Die is the definite article in Afrikaans, meaning the.

A few useful points:

• Afrikaans uses die for singular and plural nouns.
• It does not change for gender.
• It is capitalized here only because it is the first word in the sentence.

So:

• die boek = the book
• die boeke = the books
• die geldigheidsduur = the validity period

It is a compound noun, which is very common in Afrikaans.

You can break it down like this:

• geldig = valid
• -heid = -ity or -ness
• -s- = a linking sound often used in compounds
• duur = duration / period

So:

• geldig → valid
• geldigheid → validity
• geldigheidsduur → validity period / duration of validity

Afrikaans often combines ideas into one long noun instead of using a phrase with of.

This is a very common learner question.

In Afrikaans, lang and lank are related, but they are not used in exactly the same way.

A helpful rule of thumb:

• lang is commonly used before a noun: 'n lang tyd
• lank is commonly used after the verb, especially in predicate position: Die tyd is lank

So here:

• Die geldigheidsduur is lank is correct.

Compare:

• 'n lang geldigheidsduur = a long validity period
• Die geldigheidsduur is lank = the validity period is long

This is one of those patterns you get used to by seeing it often.

Because it comes after is.

In Afrikaans, adjectives usually behave differently depending on where they appear:

• Before a noun: they may take an ending
• After a linking verb like is: they usually do not

Compare:

• 'n lang geldigheidsduur
• Die geldigheidsduur is lank

So in this sentence, lank stays in its basic form because it is predicative, not directly before the noun.

Mostly yes.

Here, is is the present tense form of wees (to be), and it works very much like English is:

• Hy is moeg = He is tired
• Die kos is warm = The food is warm
• Die geldigheidsduur is lank = The validity period is long

One useful difference to remember is how negatives are formed in Afrikaans:

• Die geldigheidsduur is nie lank nie = The validity period is not long

Afrikaans uses the double nie ... nie pattern.

You invert the verb and the subject:

• Is die geldigheidsduur lank?

This is very straightforward in Afrikaans and works much like English:

• Die geldigheidsduur is lank.
• Is die geldigheidsduur lank?

So yes/no questions are often made simply by putting the verb first.

You use the Afrikaans double negative:

• Die geldigheidsduur is nie lank nie.

Pattern:

• subject + verb + nie
  • rest + nie

So:

• Hy is nie hier nie.
• Dit is nie moeilik nie.
• Die geldigheidsduur is nie lank nie.

This double nie structure is one of the most important features of Afrikaans grammar.

A good practical approach is to break it into chunks:

• gel-dig-heids-duur

A few pronunciation tips:

• The g in Afrikaans is usually a guttural sound, not the soft English g.
• heid sounds a bit like hate without the strong English diphthong.
• duur has a long vowel sound.

If you are learning to say it naturally, focus on the chunks first rather than trying to say the whole word at once.

Yes, but the compound noun is very normal and natural in Afrikaans.

Afrikaans often prefers compact compounds like:

• geldigheidsduur

instead of a longer phrase like:

• die duur van geldigheid

The compound sounds more standard and idiomatic in many contexts, especially formal or administrative language.

So for learners, Die geldigheidsduur is lank is a very useful model to remember.