Die derde tydgleuf is vanaand.

Here die means the.

In Afrikaans, die is the normal definite article for:

• singular nouns
• plural nouns
• all grammatical genders

So unlike German, Afrikaans does not change the article for masculine, feminine, or neuter nouns. It is much simpler.

Examples:

• die man = the man
• die vrou = the woman
• die kind = the child
• die kinders = the children

So in Die derde tydgleuf, die simply means the.

Because derde is an ordinal number and drie is a cardinal number.

• drie = three
• derde = third

In English, this is the difference between:

• three time slots
• the third time slot

So die derde tydgleuf means the third time slot, not the three time slot.

Some useful ordinals:

• eerste = first
• tweede = second
• derde = third
• vierde = fourth

Tydgleuf is a compound noun:

• tyd = time
• gleuf = slot / groove

So tydgleuf literally means time slot.

Afrikaans often forms nouns by joining smaller words together, just like English does with words such as timeslot, bedroom, or notebook.

Depending on context, tydgleuf can refer to:

• a scheduled appointment slot
• a place in a timetable
• a broadcast slot
• any reserved period of time

In Afrikaans, vanaand is normally written as one word, and it means tonight / this evening.

It is similar to:

• vandag = today
• vanmiddag = this afternoon
• vanmôre = this morning
• vannag = tonight / during the night

So in this sentence, vanaand is the standard spelling.

Afrikaans often uses the present tense with is to talk about scheduled future events, just as English does.

Compare English:

• The meeting is tonight.
• My flight is tomorrow.

Those are present-tense forms, but they refer to the future because the time expression makes that clear.

The Afrikaans sentence works the same way:

• Die derde tydgleuf is vanaand.

You could make the future more explicit in some contexts, but it is usually unnecessary when vanaand already shows the time.

Because that is a very natural place for a time expression in a simple statement.

The structure is:

• Die derde tydgleuf = subject
• is = verb
• vanaand = time expression

This is similar to English:

• The third time slot is tonight.

Afrikaans allows some flexibility, but this word order is straightforward and idiomatic.

A rough pronunciation guide is:

• Die ≈ dee
• derde ≈ DEHR-duh
• tydgleuf ≈ something like tayt-khlayf or tide-khlayf, depending on accent
• is ≈ iss
• vanaand ≈ fuh-NAHNT

A few pronunciation notes:

• Afrikaans d at the end of a syllable can sound softer than English learners expect.
• The g in gleuf is the typical Afrikaans guttural g/ch sound.
• The ui/eu-like vowel combinations in Afrikaans can be tricky and may vary by accent.

If you are learning to say it naturally, focus first on the rhythm: Die DER-de TYD-gleuf is va-NAAND.

Yes. Die stays the same in the plural.

Examples:

• die tydgleuf = the time slot
• die tydgleuwe = the time slots

So Afrikaans does not have separate forms like the / the plural article. It just uses die.

That makes article usage easier than in many other European languages.

Tydgleuf is correct, but depending on context, Afrikaans speakers may also use other wording.

Possible alternatives include:

• slot in informal or borrowed usage
• tydslot in some contexts
• a fuller phrase such as beskikbare tyd or afspraaktyd if the context is appointments

So tydgleuf is a good, understandable Afrikaans word, but the most natural choice can depend on whether you are talking about scheduling, broadcasting, booking, or timetables.

Yes, you could, but it changes the emphasis.

• Die derde tydgleuf is vanaand.
  This presents the third time slot as the topic and tells you when it is.

• Vanaand is die derde tydgleuf.
  This puts more emphasis on tonight.

Afrikaans often moves elements to the front for emphasis, but in normal neutral word order, the version you were given is the most straightforward.