Dit is die tandeborsel waarmee ek my tande borsel.

Dit is means This is or It is, depending on context.

In this sentence, Dit is die tandeborsel ... means This is the toothbrush ...

Afrikaans often uses dit is where English would say this is when pointing something out or identifying it.

For example:

• Dit is my boek. = This is my book.
• Dit is waar. = It is true.

So here, Dit is is simply introducing and identifying the toothbrush.

Die here means the.

So:

• die tandeborsel = the toothbrush

A useful thing to know is that Afrikaans uses die for all definite nouns, whether they are:

• singular
• plural
• common gender
• neuter

Unlike some languages, Afrikaans does not change the depending on gender.

Examples:

• die boek = the book
• die tafel = the table
• die tande = the teeth

Afrikaans often forms compound nouns by writing them as one word, just like German and sometimes like English.

So:

• tande = teeth
• borsel = brush
• tandeborsel = toothbrush

Even though English writes toothbrush as one word too, this is still worth noticing because Afrikaans does this very regularly.

Other examples:

• huisdeur = house door / front door
• skooltas = school bag
• motorfiets = motorcycle

So tandeborsel is a normal Afrikaans compound noun.

The first part of the compound comes from tande (teeth), not just tand (tooth).

That is why the word is tandeborsel.

Afrikaans compounds sometimes use a linking form that may look a little unexpected to an English speaker. In this word, tande- connects naturally to borsel.

Even though English says toothbrush, Afrikaans uses the form based on tande.

Waarmee means with which.

It is made up of:

• waar- = a relative element, like which / where / what ... with
• mee = with it / with

So:

• die tandeborsel waarmee ek my tande borsel means
• the toothbrush with which I brush my teeth

In natural English, we would usually say:

• the toothbrush that I brush my teeth with

So waarmee is a very common Afrikaans way to introduce a relative clause involving with.

In a relative clause after a noun, Afrikaans commonly uses waar- compounds such as:

• waarin = in which
• waarop = on which
• waarmee = with which
• waarvoor = for which

So after die tandeborsel, Afrikaans prefers:

• waarmee ek my tande borsel

rather than a more literal English-style structure.

This is one of the most useful patterns to learn in Afrikaans:

• die huis waarin ek woon = the house in which I live
• die stoel waarop hy sit = the chair on which he is sitting
• die pen waarmee sy skryf = the pen with which she writes

This part is a relative clause, and Afrikaans word order in subordinate clauses usually puts the main verb at the end.

So:

• waarmee ek my tande borsel literally follows the pattern:
• with which + I + my teeth + brush

Compare:

Main clause:

• Ek borsel my tande. = I brush my teeth.

Relative/subordinate clause:

• ... waarmee ek my tande borsel. = ... with which I brush my teeth.

That final verb position is very typical of Afrikaans subordinate clauses.

Because borsel can be both:

• a noun: brush
• a verb: to brush

So in this sentence:

• tandeborsel = toothbrush
• ek ... borsel = I brush

This is not unusual in Afrikaans, and English does something similar too:

• brush can be a thing
• brush can also be an action

So the repetition is perfectly natural.

My tande means my teeth.

Here, my is the normal possessive adjective, like English my before a noun:

• my boek = my book
• my hand = my hand
• my tande = my teeth

Afrikaans does not use a different form here like English mine, because mine is used without a following noun:

• This book is mine.

But before a noun, English uses my, and Afrikaans does the same:

• my tande

Because people normally brush their teeth, not just one tooth.

• tand = tooth
• tande = teeth

So:

• ek borsel my tand would mean I brush my tooth, which sounds unusual unless you are specifically talking about only one tooth.

The normal expression is:

• ek borsel my tande = I brush my teeth

Yes. The basic Afrikaans sentence is:

• Ek borsel my tande.

That is the normal, everyday way to say I brush my teeth.

In the full sentence, that clause becomes subordinate after waarmee, so the verb moves to the end:

• main clause: Ek borsel my tande.
• subordinate clause: ... waarmee ek my tande borsel.

So the meaning stays the same, but the word order changes.

Yes, you could, and it would sound natural.

That version means:

• This is the toothbrush that I use to brush my teeth.

It is a slightly different structure:

• wat ek gebruik = that I use
• om my tande te borsel = to brush my teeth

The original sentence with waarmee is a bit more direct:

• the toothbrush with which I brush my teeth

Both are good Afrikaans, but waarmee is especially useful because it teaches a very common relative-clause pattern.

A few useful things stand out:

• Dit is often pronounced quite shortly, almost like dit with a very short vowel.
• tandeborsel is a compound, so try to hear the parts: tande + borsel.
• waarmee has a long ee sound at the end.
• tande ends with -e, which is common in plural forms.

Also, in everyday speech, Dit is is often contracted to:

• Dis die tandeborsel waarmee ek my tande borsel.

That is very common in spoken and informal written Afrikaans.

The biggest grammar point is probably the use of a relative clause with a preposition, especially:

• waarmee = with which

The sentence shows how Afrikaans says:

• This is the toothbrush with which I brush my teeth.

It also shows two other important patterns:

• compound nouns: tandeborsel
• verb-final word order in subordinate clauses: ... waarmee ek my tande borsel

So this one sentence is a very good example of several core Afrikaans patterns at once.