Because Afrikaans often forms compound nouns by joining words together, much like Dutch and German.
Here:
Together:
English sometimes writes similar ideas as two words, but Afrikaans often prefers one combined word.
Other examples:
In this sentence, groot means big or large.
It usually refers to physical size here:
But groot can also have related meanings depending on context, such as grown-up, great, or important.
Examples:
In your sentence, the meaning is clearly about size.
Afrikaans adjectives are much simpler than in many other languages.
In this sentence, groot comes after the verb is, so it is being used predicatively:
In that position, the adjective normally stays in its basic form.
Compare:
Notice that groot stays groot in both of these examples.
Afrikaans does have some adjective patterns and endings in certain cases, but overall it is much simpler than Dutch or German.
Yes, but that is not a complete sentence by itself.
So die groot dansvloer is a noun phrase, not a full statement.
To make it a full sentence, you need more:
Afrikaans usually uses double negation.
So:
Notice the two nie words:
This is a very important Afrikaans pattern.
A rough English-friendly guide:
A few pronunciation notes:
If you cannot make the guttural g yet, a softer g is often understood by learners, but the real sound is made further back in the throat.
That would be:
Changes:
So unlike English, you do not change is to are here.
That is another simplification in Afrikaans:
The verb form stays the same.
Because Afrikaans verbs are much less inflected than English verbs.
With to be, the present form is is used very widely:
So in Die dansvloer is groot, you do not have to worry about matching different present-tense forms the way you do in English with am / is / are.
This is one of the reasons Afrikaans is often considered relatively straightforward grammatically.