Learn Hardcore Swahili: Wanafunzi wote huwa wanakaa kimya wakati kengele ya mtihani inalia. - All the students usually stay quiet when the exam bell rings.

Wanafunzi wote wanakaa kimya…
= The students stay / are quiet… (can be just a factual present statement; the “usually” idea depends on context.)
Wanafunzi wote huwa wanakaa kimya…
= The students usually/typically stay quiet…

So yes, “Wanafunzi wote wanakaa kimya wakati kengele ya mtihani inalia” is grammatical, but huwa makes it clearer that this is their typical behavior whenever the exam bell rings.

Isn’t huwa wanakaa redundant? Could we just say hukaa instead?

There are actually two different “habit” strategies in Swahili:

hu- + verb (no subject prefix) – more formal / textbook style:
- Wanafunzi wote hukaa kimya… = All the students stay (habitually) quiet…
huwa + [normal tense] – very common in everyday speech:
- Wanafunzi wote huwa wanakaa kimya…

So:

hukaa kimya and huwa wanakaa kimya are both acceptable.
They mean almost the same thing (“usually stay quiet”), but huwa + present is extremely common in colloquial Swahili, while hu- is more “classic grammar-book” style.

What exactly does kukaa mean here? I thought it meant “to sit”.

Kukaa has several related meanings:

to sit
- Nakaa kwenye kiti. = I sit on the chair.
to stay / remain / live (reside)
- Ninakaa Dar es Salaam. = I live in Dar es Salaam.
- Alikaa nyumbani siku nzima. = He stayed at home the whole day.
In the expression kukaa + adjective/noun, it often means “to remain/be (in a state)”:
- kukaa kimya = to stay quiet, remain silent
- kukaa tayari = to be ready (lit. stay ready)

So in wanakaa kimya, it’s not about physically sitting; it’s “they remain / keep silent.”

Why use wanakaa kimya instead of a verb like wananyamaza?

Both are possible, but they’re not identical:

kukaa kimya
- Literally: “to stay quiet.”
- Emphasizes a state of silence over some period of time.
- Perfect for “they keep quiet whenever the bell rings.”
kunyamaza
- Literally: “to become/be silent, to stop talking.”
- Emphasizes the act of falling silent or shutting up.
- Wanafunzi hunyamaza wakati kengele ya mtihani inalia.
  = The students fall silent when the exam bell rings.

In this sentence, kukaa kimya nicely matches the idea “they remain quiet” during exam time.

Is kimya an adjective or an adverb here? Why don’t we say something like kwa kimya?

In Swahili, words like kimya (silence/quiet) can function as:

a noun:
- Kulikuwa na kimya darasani. = There was silence in the classroom.
an adjectival/predicative complement after verbs like kuwa, kubaki, kukaa:
- Wako kimya. = They are quiet.
- Wanakaa kimya. = They stay/remain quiet.

Swahili doesn’t usually need a separate adverb form like English “quietly.” You don’t say kwa kimya here; kimya itself covers the idea of “in a quiet state.”

(Separate expression kimya kimya means “quietly/secretly,” but that’s a different idiom.)

What does wakati do here, and how close is it to English “when” vs “while”?

wakati literally means “time” (as a noun), but it’s often used the way English uses “when”:

wakati kengele ya mtihani inalia
= (at the) time when the exam bell rings → when the exam bell rings

It can mean either:

“at the moment when” (a point in time), or
“during the period when” (a span of time, closer to “while”),

depending on context. In this sentence, both when and while feel natural in English:

They usually stay quiet *when the exam bell rings.*
They usually stay quiet *while the exam bell is ringing.*

Could we say wakati ambapo kengele ya mtihani inalia instead? Does ambapo change the meaning?

Yes, you can say:

Wanafunzi wote huwa wanakaa kimya wakati ambapo kengele ya mtihani inalia.

ambapo is a kind of relative word (“where/when/at which”). Here it just makes the connection a bit more explicit:

wakati kengele inalia
wakati ambapo kengele inalia
→ Both mean “when the bell rings.”

The meaning is the same; ambapo sounds a bit more formal/explicit, but it’s not required.

Why is it kengele ya mtihani, not kengele wa mtihani or something else?

This is about noun class agreement in the possessive/genitive construction X ya/wa/la… Y.

The rule:
The connecting word (ya/wa/la/cha/vya…) agrees with the first noun (the one being possessed), not with the second noun.

kengele is in noun class 9/10.
- The genitive for class 9/10 is ya.
- So: kengele ya … (bell of …)
mtihani is in class 3/4 (mtihani/mitihani), but that doesn’t affect the form here; the agreement follows kengele, not mtihani.

So:

kengele ya mtihani = the exam bell (literally “bell of exam”)
If it were a class 1 noun, you’d get wa:
- mwalimu wa Kiswahili = Kiswahili teacher

Why is it kengele … inalia and not something like kengele … analia?

This is subject–verb agreement with noun classes:

kengele is class 9 (same as ndizi, nyumba, meza, etc.).
The subject prefix for class 9 (singular) in the present tense is i-.

So:

kengele inalia = the bell rings (lit. “the bell cries/sounds”)
If it were plural (kengele in class 10), you’d say:
- Kengele zinalia. = The bells ring.

a- is the subject prefix for class 1 (mtu anasoma, “the person reads”), so analia would agree with a class 1 subject (e.g. mtoto analia = the child cries), not with kengele.

Why does kulia (“to cry”) mean “to ring” here?

kulia basically means “to cry / to make a crying or ringing noise.” Swahili uses it for several kinds of sounds:

mtoto analia = the child is crying
saa inalia = the clock is striking/ringing
kengele inalia = the bell is ringing

So in this sentence, inalia is idiomatic: “the bell rings / gives out its sound.”
Another common expression is kupiga kengele = to ring a bell (lit. to strike a bell).

Can we change the word order and start with the wakati clause?

Yes. Both orders are natural:

Wanafunzi wote huwa wanakaa kimya wakati kengele ya mtihani inalia.
Wakati kengele ya mtihani inalia, wanafunzi wote huwa wanakaa kimya.

Just like English:

“The students usually keep quiet when the exam bell rings.”
“When the exam bell rings, the students usually keep quiet.”

Putting the wakati-clause first often adds a bit of emphasis to the condition/time (“As soon as / whenever the bell rings…”).

Does this sentence refer to the present, the future, or a general truth?

The structure huwa + present normally expresses general/habitual truth, not a single event:

Wanafunzi wote huwa wanakaa kimya…
= “All the students usually/always keep quiet…” (as a rule).

It’s not about just this exam or this particular bell-ringing. It describes what generally happens whenever the exam bell rings.