Afrikaans is is the present-tense form of to be, and it looks exactly like English is.
The important difference is that Afrikaans does not conjugate this verb the way English does. For example:
So is stays the same for all persons.
Because this sentence is using donker as a predicate adjective, just like in English:
The structure is:
If you put the adjective before the noun, you get a different structure:
So both are possible, but they mean slightly different things grammatically:
Usually die olie means the oil, so it refers to a specific oil already known from the context.
For example, you might be talking about oil in a pan, a bottle, or an engine.
If you wanted a more general meaning, Afrikaans can sometimes leave out the article, depending on context. But with die, the sentence most naturally means that particular oil is dark.
No. Afrikaans does not use grammatical gender the way some other European languages do.
So with olie, you do not need to learn whether it is masculine, feminine, or neuter. You simply use die for the.
That makes sentences like Die olie is donker simpler to build than their equivalents in many other languages.