Learn Hardcore Swahili: Mpango wa mtihani unaweza kubadilishwa na mwalimu. - The exam plan can be changed by the teacher.

Summary:
It is wa because it agrees with mpango (class 3), not with mtihani. The form of this “of” word depends on the class and number of the first noun.

Why is it unaweza and not anaweza or inaweza?

The verb unaweza must agree with the subject of the sentence, which is mpango:

Mpango = class 3 (m-/mi-),
Class 3 subject prefix in the present tense is u-.

So the structure is:

u- (subject prefix for class 3, referring to mpango)
-na- (present tense marker)
weza (root: be able, can)

→ u-na-weza → unaweza = it can / it is able to.

If the subject were a person (class 1), for example mwalimu, you’d use a-:

Mwalimu anaweza… = The teacher can…

If the subject were plural mipango (plans, class 4), you’d use i-:

Mipango inaweza kubadilishwa… = The plans can be changed…

So:

unaweza agrees with mpango (class 3),
anaweza would agree with a singular person (class 1),
inaweza would agree with class 4 (e.g. mipango) or some other non-human classes, depending on the noun.

How is unaweza built up morphologically?

Unaweza is a good example of standard Swahili verb structure:

u- = subject prefix for class 3 singular (referring to mpango)
-na- = present tense marker (general present / present habitual)
weza = verb root meaning be able / can

So:

u-na-weza → unaweza = it can / it is able to (right now / in general).

A rough pattern is:

Subject prefix + Tense/Aspect marker + Verb root

Some related forms you might see:

utakuwa (it will be): u-
- -ta- (future) + kuwa (to be)
ungeweza (it could / would be able): u-
- -nge- (conditional) + weza

What is the function of ku- in kubadilishwa?

In kubadilishwa, the ku- at the beginning is the infinitive marker:

badilishwa = be changed
ku-badilishwa = to be changed

Swahili uses ku- like English to in to change, to eat, to go.
When you have a modal-like verb such as kuweza (to be able), it is very common to follow it with an infinitive:

unaweza kula = it can eat / you can eat
unaweza kuja = you can come
unaweza kubadilishwa = it can be changed

So the full structure is like English:

unaweza (it can) + kubadilishwa (to be changed)
→ it can be changed

What is the difference between kubadilisha, kubadilika, and kubadilishwa?

All three come from the same root idea badili (change), but they differ in voice and valency:

kubadilisha – to change (something)
- This is transitive: someone changes something.
- Example:
  - Mwalimu anaweza kubadilisha mpango.
    The teacher can change the plan.
kubadilika – to change / to become different (by itself)
- This is more intransitive or middle voice: something changes on its own / undergoes change, no explicit agent.
- Example:
  - Mpango wa mtihani unaweza kubadilika.
    The exam plan can change (may change, may end up different).
kubadilishwa – to be changed (by someone)
- This is passive: the thing is changed by an agent.
- Example (your sentence pattern):
  - Mpango wa mtihani unaweza kubadilishwa na mwalimu.
    The exam plan can be changed by the teacher.

So:

kubadilisha: X changes Y.
kubadilika: Y changes (no explicit X).
kubadilishwa: Y is changed by X.

Does na in na mwalimu really mean by? I thought na meant and.

na does several jobs in Swahili, and the meaning depends on context:

“and” (joining words/phrases):
- mwalimu na mwanafunzi = teacher and student.
“with” (accompaniment or instrument):
- Ninaenda na rafiki yangu. = I am going with my friend.
“by” (agent of a passive verb) – this is the usage in your sentence:
- Mpango wa mtihani unaweza kubadilishwa na mwalimu.
  Here na mwalimu = by the teacher (the agent who performs the action).

So yes, in a passive construction, na + noun is how you say “by X” (the doer of the action).

Could I say Mwalimu anaweza kubadilisha mpango wa mtihani instead? Is the meaning the same?

Yes, you can, and it is very natural Swahili. The difference is voice and emphasis:

Active voice:
- Mwalimu anaweza kubadilisha mpango wa mtihani.
  → Subject: mwalimu (teacher)
  → Verb: anaweza kubadilisha (can change)
  → Object: mpango wa mtihani (exam plan)
  Emphasis tends to be on what the teacher can do.
Passive voice (your original style):
- Mpango wa mtihani unaweza kubadilishwa na mwalimu.
  → Subject: mpango wa mtihani (exam plan)
  → Verb: unaweza kubadilishwa (can be changed)
  → Agent: na mwalimu (by the teacher)
  Emphasis tends to be on the exam plan and its ability to be changed.

Both are grammatically fine and convey essentially the same factual information.
Choice of active vs passive depends on what you want to foreground: the teacher (active) or the plan (passive).

Where is the tense/time in this sentence? How would I say “could be changed” or “will be changed”?

The tense/aspect is carried inside unaweza:

u- = class 3 subject prefix (for mpango)
-na- = present tense marker
weza = be able

So unaweza means can / is able (now/in general).

To change the time or mood, you mainly adjust the tense/aspect marker or use different forms of kuweza:

uliweza kubadilishwa = it was able to be changed / it could be changed (past ability)
- u- (class 3) + -li- (past) + weza
utaweza kubadilishwa = it will be able to be changed / it will be changeable
- u-
  - -ta- (future) + weza
ungeweza kubadilishwa = it could be changed / would be able to be changed (conditional)
- u-
  - -nge- (conditional) + weza

The infinitive part kubadilishwa stays the same; the tense is encoded in the finite verb (u- + tense + weza) before it.

If I make everything plural, how does the sentence change?

Let’s pluralize both mpango and mtihani:

mpango (plan, class 3) → mipango (plans, class 4)
mtihani (exam, class 3) → mitihani (exams, class 4)

Now we need agreement changes:

Head noun is now mipango (class 4), so the genitive marker changes:
- mipango ya mitihani = plans of the exams / exam plans.
Subject is now plural class 4, so the subject prefix on the verb changes from u- to i-:
- inaweza instead of unaweza:
  - i- (class 4 subject) + -na- (present) + weza (be able).

The rest stays the same:

Mipango ya mitihani inaweza kubadilishwa na mwalimu.
= The exam plans can be changed by the teacher.

Notice how:

mpango wa … unaweza → singular
mipango ya … inaweza → plural

Why isn’t mwalimu affecting the verb agreement? Shouldn’t the verb agree with the person (teacher)?

In Swahili, the verb agrees with the grammatical subject, not with whoever does the action in meaning.

In your passive sentence:

Mpango wa mtihani = grammatical subject (class 3, singular)
unaweza kubadilishwa = verb with subject prefix u- agreeing with mpango
na mwalimu = the agent (the doer), but introduced by na after a passive

So even though in real life the teacher is doing the changing, grammatically the plan is the subject, so the verb matches mpango (class 3), not mwalimu (class 1).

If you switch to the active voice:

Mwalimu anaweza kubadilisha mpango wa mtihani.
Now mwalimu is the subject (class 1), so the verb uses a- (anaweza).

Can I move na mwalimu to another place in the sentence, like earlier?

In practice, na + agent in a passive sentence almost always comes after the verb phrase. The natural orders are:

Mpango wa mtihani unaweza kubadilishwa na mwalimu.
Mpango wa mtihani unaweza kubadilishwa. (just omit the agent)

Putting na mwalimu before the verb, e.g.:

✗ Mpango wa mtihani na mwalimu unaweza kubadilishwa

would sound confusing or incorrect, because na mwalimu before the verb is likely to be heard as “the exam plan and the teacher” (a coordinated subject), which does not match the verb agreement.

So for an agent after a passive verb, keep na mwalimu after the passive verb phrase.

What role do noun classes play in this sentence overall?

Noun classes drive agreement all over this sentence:

mpango – class 3 (m-/mi-)
- Controls:
  - Subject prefix on the verb: u- in unaweza
  - Form of the genitive “of”: wa in mpango wa mtihani
mtihani – also class 3, but here used as the second noun in the “X of Y” structure:
- It does not control wa; wa agrees with mpango, the head noun.
mwalimu – class 1 (m-/wa-), but here only appears in a prepositional phrase (na mwalimu) as the agent of a passive:
- It does not affect verb agreement, because it’s not the grammatical subject.

So in this sentence, noun classes are crucial for:

choosing wa (not ya, la, cha, etc.),
choosing u- as the subject prefix (not a-, i-, etc.).

If you change the nouns to different classes or to plural, you must update these agreement elements to match.