Ons gebruik insekweerder, tensy daar geen muskiete is nie.

Tensy means unless.

It introduces an exception to the main statement:

• Ons gebruik insekweerder = We use insect repellent
• tensy daar geen muskiete is nie = unless there are no mosquitoes

So the basic idea is: we do this, except if that condition applies.

Because tensy introduces a subordinate clause.

In Afrikaans, subordinate clauses usually send the finite verb to the end:

• Main clause: Daar is geen muskiete nie
• After tensy: tensy daar geen muskiete is nie

So this is normal Afrikaans word order after a subordinating conjunction such as tensy, as, omdat, dat, and wanneer.

Here daar is the existential there, like in English there are no mosquitoes.

It does not mean a physical place in this sentence. It is just used to express existence or presence.

Compare:

• Daar is muskiete. = There are mosquitoes.
• Daar is geen muskiete nie. = There are no mosquitoes.

So daar is very common in sentences about what is or is not present.

Afrikaans often uses a two-part negative structure.

With nouns, geen means no / not any, and the clause is usually also closed off with nie at the end:

• Daar is geen muskiete nie. = There are no mosquitoes.
• Ek het geen tyd nie. = I have no time.

So geen carries the main negative meaning for the noun, and the final nie is part of standard Afrikaans negation.

This can feel unusual to English speakers, because English normally uses only one negative word here.

Because geen is used directly before the noun, without an article.

So you say:

• geen muskiete = no mosquitoes
• geen muskiet = no mosquito

You do not say geen die muskiete or geen 'n muskiet.

This is similar to English no mosquitoes, where you also do not use an article.

Because the sentence is talking about mosquitoes in general, not one specific mosquito.

• muskiet = mosquito
• muskiete = mosquitoes

In a sentence like this, the plural is the natural choice:

• Daar is geen muskiete nie. = There are no mosquitoes.

Using the singular would sound more like not a single mosquito, which is possible in some contexts, but the plural is the normal general statement.

Because Afrikaans verbs usually do not change form according to the subject in the present tense.

So:

• ek gebruik
• jy gebruik
• ons gebruik
• hulle gebruik

All use the same verb form: gebruik.

This is much simpler than English, where you get forms like I use but he uses.

Because Afrikaans usually writes compound nouns as a single word.

So:

• insek = insect
• weerder = repeller / something that wards off

Together:

• insekweerder = insect repellent

This is very common in Afrikaans. English often writes similar ideas as two words, but Afrikaans prefers one compound word.

In this sentence, insekweerder is being used in a general sense, like a substance or product category:

• Ons gebruik insekweerder = We use insect repellent

That is similar to English, where you can say We use insect repellent without an.

If you wanted to talk about one particular repellent product, you could say:

• Ons gebruik 'n insekweerder.

So both are possible, but they are used a little differently.

No, not if you want the same meaning.

• tensy = unless
• as = if

These are different:

• Ons gebruik insekweerder, tensy daar geen muskiete is nie. = We use insect repellent, unless there are no mosquitoes.
• Ons gebruik insekweerder as daar geen muskiete is nie. = We use insect repellent if there are no mosquitoes.

The second sentence changes the meaning completely.

It is the most natural and common way in a sentence like this.

Afrikaans often prefers geen + noun for no / not any:

• geen muskiete
• geen geld
• geen tyd

You may sometimes see other negative patterns in Afrikaans, but for a noun phrase like this, geen is the standard and most idiomatic choice.

So daar geen muskiete is nie is exactly the kind of structure you should get used to.

Because the sentence has a main clause followed by a subordinate clause, and Afrikaans normally separates these with a comma in writing:

• Ons gebruik insekweerder, tensy daar geen muskiete is nie.

The comma helps show that the second part is an exception to the first part. It is a normal punctuation choice in standard written Afrikaans.