As jy die antwoord weet, sê dit dadelik.

Because as introduces a subordinate clause in Afrikaans, and in subordinate clauses the verb typically goes to the end.

So:

• jy weet die antwoord = you know the answer
• As jy die antwoord weet = if you know the answer

This is very common in Afrikaans after words like as (if), dat (that), omdat (because), and wanneer (when).

Here, as means if.

In Afrikaans, as often introduces a condition:

• As jy kom, sal ek bly wees. = If you come, I’ll be happy.

In some contexts English might naturally translate it more like when, depending on meaning, but in this sentence the basic function is conditional: if you know the answer.

The comma separates the subordinate clause from the main clause:

• As jy die antwoord weet, = subordinate clause
• sê dit dadelik. = main clause

Afrikaans commonly uses a comma after an introductory subordinate clause like this.

Because this is an imperative, meaning a command.

In Afrikaans, commands usually use just the verb without an expressed subject:

• Sê dit! = Say it!
• Kom hier! = Come here!

So sê dit dadelik means say it immediately. The subject jy is understood, just like English Tell me! or Come here!

Dit means it.

It refers back to the thing already mentioned or understood from context. In this sentence, it stands for die antwoord.

So instead of repeating die antwoord, Afrikaans uses the pronoun:

• As jy die antwoord weet, sê die antwoord dadelik.
  This is possible in some contexts, but it sounds repetitive.
• As jy die antwoord weet, sê dit dadelik.
  This is the natural phrasing.

Die is the normal definite article in Afrikaans, used for the.

Unlike English, Afrikaans does not change the article for gender or number:

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

So die antwoord simply means the answer.

Yes, dadelik means immediately, at once, or right away.

It gives a sense of doing something without delay.

Examples:

• Kom dadelik hierheen! = Come here immediately!
• Ek sal dit dadelik doen. = I’ll do it right away.

So in this sentence, it strengthens the command: say it as soon as you know it.

Yes. You could say:

Sê dit dadelik as jy die antwoord weet.

That is also grammatical and natural.

The difference is mostly one of emphasis and flow:

• As jy die antwoord weet, sê dit dadelik.
  Starts with the condition.
• Sê dit dadelik as jy die antwoord weet.
  Starts with the command.

Both mean essentially the same thing.

Afrikaans does not need dan here, even though English sometimes uses then in similar conditional structures.

So:

• As jy die antwoord weet, sê dit dadelik. = If you know the answer, say it immediately.

You could sometimes add dan in other sentences for emphasis, but it is not necessary here, and leaving it out is perfectly normal.

Sê is the verb to say / tell.

The circumflex on ê shows the vowel sound and helps distinguish the spelling. In writing, it is part of the standard form of the word.

Some common forms are:

• sê = say / tells / to say
• Ek sê = I say
• Hy sê = he says

Afrikaans verbs do not change much compared with English, which makes them easier to learn.

You would need an expressed subject in the main clause. For example:

• As jy die antwoord weet, sê jy dit dadelik. = If you know the answer, you say it immediately.

That is a statement, not a command.

Compare:

• sê dit dadelik = say it immediately (command)
• jy sê dit dadelik = you say it immediately (statement)

In this sentence, antwoord is a noun: the answer.

But antwoord can also be a verb in Afrikaans:

• die antwoord = the answer
• Ek antwoord hom. = I answer him.

That is something learners often notice because English also has answer as both a noun and a verb.

Here, the article die shows clearly that antwoord is being used as a noun.