Kwa sababu ya ukungu, sioni barabara vizuri.

Kwa sababu ya means because of.

It is a fixed expression made from:

• kwa = by / through / because of in some expressions
• sababu = reason
• ya = of

So literally, it is something like by reason of or for the reason of.

In this sentence:

• kwa sababu ya ukungu = because of the fog

This is a very common way to give a reason in Swahili.

The word ukungu means fog or mist.

The u- at the beginning is part of the noun itself, not a separate word. Many Swahili nouns belong to noun classes, and ukungu is one of those nouns whose form includes u-.

So you should learn it as a whole word:

• ukungu = fog

You generally should not remove the u-.

Sioni means I do not see or, in context, I can’t see.

In this sentence, English would naturally translate it as:

• I can’t see the road well or
• I don’t see the road clearly

Because the problem is fog, English often uses can’t even though the Swahili verb is simply negative.

Sioni comes from the verb kuona = to see.

In the present negative, Swahili changes the verb in a special way:

• the negative subject marker for I is si-
• the verb ends in -i instead of -a

So:

• kuona = to see
• naona = I see / I am seeing
• sioni = I do not see

A helpful breakdown is:

• si- = I do not
• -on- = see
• -i = negative present ending

Because Swahili does not usually form the present negative by simply adding si to the positive present.

Positive:

• naona = I see

Negative:

• sioni = I do not see

So the negative present has its own pattern. You do not say sinaona for I do not see.

This is an important pattern to memorize:

• nina / si- patterns are not always direct opposites in every tense
• present negative often uses a special form like sioni, sisemi, sifanyi, etc.

Because barabara is the direct object of the verb sioni.

The basic order here is:

• reason phrase
• verb
• object
• adverb

So:

• Kwa sababu ya ukungu = because of the fog
• sioni = I do not see
• barabara = the road
• vizuri = well / clearly

This word order is very natural in Swahili.

It can mean either road or the road, depending on context.

Swahili does not have articles like a, an, and the. So:

• barabara can mean a road, the road, or just road in a general sense

In this sentence, English naturally says:

• the road

because the speaker is probably talking about the road they are on or looking at.

Vizuri means well.

In this sentence, it functions like an adverb, so the whole ending:

• sioni barabara vizuri means
• I do not see the road well or more naturally,
• I can’t see the road clearly

So vizuri describes how the speaker sees.

Because nzuri is usually the adjective form, meaning good or nice, while vizuri is commonly used as an adverb meaning well.

Compare:

• barabara nzuri = a good road
• naona vizuri = I see well

So in this sentence, we need the adverb:

• vizuri

Yes. The comma is helpful in writing, but it is not essential.

You can write:

• Kwa sababu ya ukungu sioni barabara vizuri.

The comma simply marks a pause after the introductory reason phrase:

• Because of the fog, ...

So the meaning stays the same with or without the comma.

Yes, Swahili allows some flexibility.

For example, you could also say:

• Sioni barabara vizuri kwa sababu ya ukungu.

This still means:

• I can’t see the road well because of the fog.

The original version puts the reason first:

• Kwa sababu ya ukungu, ...

That gives a little more emphasis to the cause.

It can mean both.

Depending on context, sioni may be:

• I do not see
• I can’t see

In this sentence, because of ukungu (fog), English usually prefers:

• I can’t see the road well

But grammatically, the Swahili form itself is simply negative present.

The dictionary form is kuona, which means to see.

In Swahili, verbs are usually listed with ku-:

• kuona = to see
• kula = to eat
• kusoma = to read

So when you want to look up sioni, you should look for kuona.

Yes, it is completely natural.

Kwa sababu ya ukungu, sioni barabara vizuri. is a normal and clear way to say that fog is making it hard to see the road.

A Swahili speaker would understand it easily, and it sounds appropriate in everyday speech.