Yes. 'n is the Afrikaans indefinite article, so it means a or an.
Afrikaans does not change it depending on the next sound. English has a button but an apple; Afrikaans uses 'n in both kinds of situations.
So:
The apostrophe is just part of the normal spelling of the Afrikaans indefinite article.
A few practical points:
Also, even at the beginning of a sentence, 'n itself stays lowercase. For example:
The next word gets the capital letter, not 'n.
Knoop can mean more than one thing, depending on context.
Common meanings include:
In a clothing sentence like Die manchet het 'n knoop, the natural meaning is button, because cuffs commonly have buttons.
So even though knoop can literally mean knot, context points you to the correct meaning.
Yes, in this sentence it is very similar to English:
So the structure is:
subject + verb + object
That said, Afrikaans is often described as a verb-second language in main clauses. In this example, the subject comes first, so the sentence ends up looking very English-like.
You cannot tell from die alone, because die can be used with both singular and plural nouns.
So number is usually understood from:
In this sentence, the intended meaning is singular: the cuff. The important thing to notice is that die does not by itself tell you singular vs. plural.
Yes, normally you do.
Knoop here is a singular countable noun, so Afrikaans usually needs an article or another determiner before it, just as English does:
So het knoop would sound incomplete here, while het 'n knoop is the normal form.
In this sentence, het is the main verb and means has. But het is also very commonly used as an auxiliary verb in the past tense:
So learners often see het in two roles:
In Die manchet het 'n knoop, it is the first type: a main verb meaning has.