Die rubberseël is nat.

Yes. die is the Afrikaans definite article, so here it works like English the.

A few useful things to know:

• Afrikaans does not have grammatical gender like German.
• So die is used for all definite nouns, not different words for masculine/feminine/neuter.
• die is also used for the plural definite article.

Examples:

• die rubberseël = the rubber seal
• die rubberseëls = the rubber seals

Because Afrikaans usually writes compound nouns as one word.

So:

• rubber
  • seël → rubberseël

This is very common in Afrikaans. English often writes these as two words or with a space, but Afrikaans normally joins them.

The last part is the main noun:

• seël = the basic thing
• rubber- = tells you what kind of seal it is

So rubberseël means a kind of seël made of or related to rubber.

Here is is the present-tense form of to be.

A very useful feature of Afrikaans is that this form does not change the way English does.

So you get:

• ek is = I am
• jy is = you are
• hy/sy is = he/she is
• ons is = we are
• hulle is = they are

So is can correspond to English am / is / are, depending on the subject.

Because nat is the adjective describing the subject after the linking verb is.

The structure is:

• Die rubberseël = subject
• is = linking verb
• nat = adjective/complement

This is very similar to English:

• The rubber seal is wet.

So the word order here is normal and natural Afrikaans.

In this sentence, nat is used after the verb is, so it stays in its basic form.

This is called a predicative adjective: it comes after a linking verb and describes the subject.

Examples:

• Die vloer is nat.
• Die handdoek is droog.
• Die rubberseël is nat.

So in this kind of sentence, the adjective is usually just the plain dictionary form.

The ë shows that the vowels are pronounced separately, not as one combined vowel sound.

That means seël has two syllables rather than being read as a single ee sound unit.

So the dots are not decorative—they tell you something about pronunciation and syllable division.

This kind of marking is fairly important in Afrikaans spelling.

A rough English-friendly guide would be:

• Die ≈ dee
• rubberseël ≈ RUB-er-see-uhl
• is ≈ iss
• nat ≈ nuht / naht depending on accent

So roughly:

dee RUB-er-see-uhl iss nuht

That is only an approximation, but it gives the general shape.

Yes, in this simple sentence it is very close to English:

• Die rubberseël = subject
• is = verb
• nat = complement

So it follows:

Subject + verb + adjective

However, one important broader rule in Afrikaans is that the finite verb usually stays in the second position in a main clause.

For example:

• Die rubberseël is nat.
• Vandag is die rubberseël nat.

So even if something else comes first, the verb still tends to stay second.

No. Unlike German, ordinary nouns are not capitalized in Afrikaans.

So:

• die rubberseël is nat would only have a capital D at the start because it begins the sentence.
• rubberseël and nat stay lowercase.

You capitalize:

• the first word of a sentence
• proper names
• certain special cases, as in English

Yes. nat can cover a range like English wet, damp, or moist, depending on context.

So the exact strength depends on the situation:

• a slightly damp seal could be nat
• a clearly wet seal could also be nat

If a speaker wants to be more specific, the surrounding context usually makes that clear.

Usually, for this sentence, die is the natural choice if you mean a specific rubber seal.

So:

• Die rubberseël is nat. = The rubber seal is wet.

If you remove die, it can sound less natural or more like a label, headline, or very general statement rather than a normal full sentence about a particular object.

So for ordinary everyday use, keep die here.