Wakiwa wamekula chakula cha jioni, watoto wanakaa kwenye kochi sebuleni.

Wakiwa means something like while they are, when they are, or in this sentence more naturally once they are / after they have.

It is built from:

• wa- = they
• -ki- = a marker often used for while/when/if
• -wa = be

So wakiwa literally has the idea of while they are being/in the state of.
Because it is followed by wamekula (they have eaten), the whole phrase wakiwa wamekula means when they have eaten or after they have eaten.

Both can work, but they are slightly different in feel.

• baada ya kula chakula cha jioni = after eating dinner
• wakiwa wamekula chakula cha jioni = once they have eaten dinner / when they’ve eaten dinner

The version with wakiwa wamekula emphasizes the state resulting from a completed action: the children are now in the condition of having eaten.

So it is a very natural way to connect one completed action with what happens next.

Wamekula breaks down like this:

• wa- = they
• -me- = perfect marker, often meaning have
• -kula = eat

So wamekula means they have eaten.

This is one of the most useful Swahili verb patterns to learn:

• nimekula = I have eaten
• umekula = you have eaten
• amekula = he/she has eaten
• wamekula = they have eaten

Because cha must agree with chakula.

Chakula belongs to noun class 7, and the possessive/connector form for that class is cha.

So:

• chakula cha jioni = food of the evening = dinner/evening meal

If the noun were from a different class, the connector would change. For example:

• kitabu cha mwanafunzi = the student’s book
• meza ya mwanafunzi = the student’s table

So cha is not random; it is there because chakula requires it.

Yes, in context it means dinner or evening meal.

Literally, it is:

• chakula = food/meal
• cha jioni = of the evening

So the full expression is evening meal.
That is the normal Swahili way to say dinner.

Here wanakaa means they sit or they are sitting/staying.

The verb kaa can mean different things depending on context:

• sit
• stay
• live
• remain

In this sentence, because of kwenye kochi sebuleni, the meaning is clearly about being seated or settled on the couch.

So the natural translation is something like:

• the children sit on the couch in the living room
• the children are sitting on the couch in the living room

It can be either, depending on context.

The -na- tense in Swahili often covers both:

• present continuous: are sitting
• habitual/general present: sit

So wanakaa could mean:

• they are sitting
• they sit
• they usually sit

In a single standalone sentence like this, English translation depends on the situation. If this is describing a scene, are sitting may sound more natural. If it is describing a routine, sit may be better.

Kwenye is a very common locative word meaning on, in, or at, depending on context.

So:

• kwenye kochi = on the couch

Swahili often uses locative words more flexibly than English. English makes a sharper distinction between on, in, and at, but Swahili kwenye can cover several of these meanings, and the noun tells you which English preposition sounds best.

With kochi, the natural English choice is on the couch.

Sebuleni means in the living room.

It comes from:

• sebule = living room
• -ni = a locative ending meaning in/at/to

So:

• sebule = living room
• sebuleni = in the living room

This -ni ending is very common in place words:

• nyumbani = at home
• shuleni = at school
• mjikoni = in the kitchen
• sebuleni = in the living room

Because they give two different layers of location:

• kwenye kochi = the specific place: on the couch
• sebuleni = the larger place: in the living room

So the sentence is very natural: it tells you both what they are on and where that couch is.

English does the same thing:

• on the couch in the living room

Swahili does not have articles like the or a/an.

So watoto can mean:

• children
• the children

The exact meaning depends on context.

That is why a Swahili sentence can often be translated into English in more than one natural way. English requires an article in many places, but Swahili usually does not.

Yes, to some extent.

The sentence begins with the subordinate/background clause:

• Wakiwa wamekula chakula cha jioni = After they have eaten dinner
• watoto wanakaa kwenye kochi sebuleni = the children sit on the couch in the living room

Putting the when/after clause first is very natural because it sets the scene before the main action.

You could also express the idea differently, for example with baada ya:

• Baada ya kula chakula cha jioni, watoto wanakaa kwenye kochi sebuleni.

That would still be natural, but the original sentence is perfectly good Swahili.

Because Swahili often uses both the full noun and the subject marker.

The markers in:

• wakiwa
• wamekula
• wanakaa

already show a they subject, but watoto is still stated explicitly so the sentence is clear and complete.

This is very normal in Swahili. The noun gives the listener the actual subject, and the verb agrees with it.

So the structure is not redundant in a bad way; it is just standard grammar.