Die sosiale groep is groot.

Die is the Afrikaans definite article, so here it means the.

A useful thing to know is that Afrikaans does not change the definite article for gender, as languages like German do. Die is used very broadly for singular and plural nouns.

So in Die sosiale groep is groot, die simply marks groep as the group.

Because the adjective comes before the noun.

In Afrikaans, an adjective used attributively—that is, directly before a noun—usually takes an -e ending.

• sosiaal = social
• die sosiale groep = the social group

So sosiale is the form you expect before groep.

Because groot comes after the verb is, so it is being used predicatively, not before a noun.

In Afrikaans:

• Before a noun, many adjectives take -e: die groot groep
• After is, the adjective usually stays in its basic form: Die groep is groot

So:

• die sosiale groep = the social group
• is groot = is big

That difference—before the noun versus after the verb—is the key reason.

Yes, in this simple main clause it is very similar to English:

• Die sosiale groep = the social group
• is = is
• groot = big

So the structure is:

subject + verb + adjective

That makes the sentence very straightforward for an English speaker.

Mostly yes. Is is the present-tense form of to be in Afrikaans.

A very helpful difference from English is that Afrikaans does not change the verb to be for different persons in the present tense the way English does.

For example:

• Ek is = I am
• Jy is = you are
• Hy is = he is
• Ons is = we are

So is is used much more widely than English is.

Here, groep is singular: group.

If it were plural, it would usually be groepe:

• die groep = the group
• die groepe = the groups

Even though die can be used for both singular and plural, groep itself tells you this sentence is singular.

A rough guide for an English speaker is:

Die sosiale groep is groot
≈ dee so-see-AA-luh khroop is khroht

A few notes:

• die is usually pronounced like dee, not like English die
• sosiale has several syllables: so-si-a-le
• g in Afrikaans is often a throaty sound, not the English g
• groot rhymes more with a long oat-type sound than with English root

Pronunciation varies a bit by speaker and region, but this will get you close.

Yes. Groot often means big or large, but depending on context it can also suggest important, major, or great.

In this sentence, without extra context, the most natural reading is simply:

The social group is big.

But in a different context, it could imply that the group is significant or influential.

Because normal Afrikaans capitalization works much like English capitalization in ordinary sentences.

In Die sosiale groep is groot:

• Die is capitalized because it begins the sentence
• sosiale, groep, is, and groot are not capitalized because they are common words, not proper nouns

So the capitalization here is completely normal.

Not in the same way as many other European languages.

Afrikaans does not require you to learn different definite articles like masculine, feminine, and neuter forms. That is one reason sentences like this are relatively simple:

• die groep
• die tafel
• die man
• die vrou

They all use die as the definite article.

So for an English speaker, Afrikaans noun grammar is usually easier than German or Dutch in this respect.

Yes, grammatically you could, but it does not mean exactly the same thing.

• Die sosiale groep is groot = The social group is big
  Here, sosiale identifies what kind of group it is.
• Die groep is sosiaal en groot = The group is social and big
  Here, sosiaal describes the group itself as sociable or social.

So the original sentence is about a type of group, not about the group’s behavior.

The dictionary form is sosiaal.

When you look words up, adjectives are usually listed in their base form. Then, when they come before a noun, they often take the -e ending:

• dictionary form: sosiaal
• before noun: sosiale groep

So if you wanted to memorize the vocabulary, you would usually learn:

• sosiaal = social
• groep = group
• groot = big / large

Yes, it is grammatical and natural.

It is a very clear, simple sentence that shows several common Afrikaans patterns:

• die for the
• an adjective before the noun: sosiale groep
• is as the present tense of to be
• a predicate adjective after the verb: groot

So it is a good example sentence for learning basic Afrikaans structure.