Learn Hardcore Swahili: Siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma. - Not only is our teacher strict, but she/he is also compassionate.

si – base negative copula (“is not/are not”)
- Huyu si mwalimu. = This one is not a teacher.
sio and siyo – pronounced the same in many accents; both often used to emphasize or make the negation a bit clearer/stronger, especially before a noun phrase:
- Sio mwalimu, ni daktari. = Not a teacher, (he’s) a doctor.
- Siyo rahisi. = It’s not easy.

In patterns like “not only … but also …”, you will frequently see:

Si tu … bali pia …
Sio tu … bali pia …
Siyo tu … bali pia …

All three appear in real usage. Siyo tu (as in your sentence) is very common and totally correct.

Why is there no subject pronoun like yeye (“he/she”) in the sentence?

Swahili usually drops subject pronouns when they’re clear from context. The verb or copula form, plus context, already shows who we’re talking about.

In your sentence:

Siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma.

There is no explicit yeye, but it’s understood:

(Yeye) siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma.
= (He/She) is not only our strict teacher, but is also compassionate.

You can add yeye for extra clarity or emphasis:

Yeye siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma.

but it isn’t required.

Why isn’t there ni before mwalimu wetu mkali? Can I say “Siyo tu ni mwalimu wetu mkali …”?

In Swahili, after si/si-o/si-yo plus a noun, ni is usually not used:

Si mwalimu. = He/She is not a teacher.
(not Si ni mwalimu)

In your sentence:

Siyo tu mwalimu wetu mkali
= (Literally) “(He/She) is not only our strict teacher”

Putting ni there (Siyo tu ni mwalimu wetu mkali) sounds unnatural/wrong to most speakers.

But notice that in the positive part, ni appears:

bali pia ni mwenye huruma
= but also is compassionate

So the pattern is:

Si/Sio/Siyo + (tu) + [NOUN PHRASE], without ni
… bali pia ni + [NOUN PHRASE / mwenyé-phrase], with ni

Why is it mwalimu wetu mkali and not mwalimu mkali wetu? What’s the word order?

Swahili has a fairly fixed order for elements after a noun:

Noun
Possessive (my/our/their, etc.)
Adjective(s)

So:

mwalimu = teacher
wetu = our
mkali = strict

Correct order:

mwalimu wetu mkali = our strict teacher

Other examples:

rafiki wangu mzuri = my good friend
kitabu chao kipya = their new book

So mwalimu mkali wetu is ungrammatical in standard Swahili.

What is the difference between bali and lakini? Why use bali here?

Both bali and lakini mean something like “but”, but they’re used differently:

lakini = “but” in the general contrast sense:
- Nilitaka kwenda, lakini nilikuwa na kazi.
  I wanted to go, but I had work.
bali = “but rather / but instead / but (on the contrary)”
It usually corrects or contrasts with a previous negative or limitation.

In the pattern “not only X, but also Y”, Swahili prefers bali:

Siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma.

Here, bali picks up after the “not only” part and adds the second positive trait. Using lakini would feel less idiomatic in this specific structure.

Can I say lakini pia instead of bali pia?

You’ll definitely hear lakini pia in general speech:

Ni mwerevu, lakini pia ni mchapakazi.
He’s clever, but he’s also hardworking.

However, with the specific “not only … but also …” structure, bali pia is the more standard and elegant choice:

Siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma. ✅ (best)
Siyo tu mwalimu wetu mkali, lakini pia ni mwenye huruma. ✅ (understood, but less textbook-like)

So: lakini pia is grammatical and clear, but bali pia better matches this contrast pattern with siyo tu / si tu.

What does mwenye huruma literally mean, and how does it function?

Mwenye huruma is a common descriptive phrase:

mwenye = one who has / possessing
huruma = compassion, pity, mercy

Literal meaning: “one who has compassion”
Natural translation: “compassionate / kind-hearted / merciful”

In the sentence:

… bali pia ni mwenye huruma.
= but also (he/she) is compassionate.

The mwenye + [noun] construction is widely used to create adjectives from nouns:

mwenye furaha = joyful (one who has joy)
mwenye hasira = angry / hot-tempered (one who has anger)
mwenye heshima = respectful (one who has respect)

It behaves like a descriptive adjective for the person.

Does mwenye agree with the noun class? Why do we see mwenye and not some other form?

Yes, mwenye comes from an agreeing stem -enye, which changes slightly with noun classes. For the “person” classes (m-/wa-), the common singular form is mwenye.

Some examples:

mtu mwenye huruma = a compassionate person
mwalimu mwenye huruma = a compassionate teacher
wanafunzi wenye adabu = well-mannered students

In your sentence, the subject (he/she) is a person (implied mtu / mwalimu), so mwenye huruma is the appropriate form.

Because the subject is already understood, we just say:

… ni mwenye huruma
= (he/she) is one who has compassion.

Why do we repeat ni in bali pia ni mwenye huruma? Could we say “bali pia mwenye huruma”?

Ni is the positive copula “is/are”. In coordinated structures, Swahili often repeats the copula for clarity and balance:

Yeye ni mwalimu, na ni mwanafunzi pia.
He is a teacher, and also a student.

In your sentence:

Siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma.

The first part already has an implied “to be” (through siyo), so in the second part we explicitly add ni again.

If you say … bali pia mwenye huruma (without ni), people will still understand, but it sounds a bit less complete/natural. The standard, smooth version keeps ni.

Can I change the word order to Mwalimu wetu siyo tu mkali, bali pia mwenye huruma? Is that still correct?

Yes, that version is both grammatical and natural, but it slightly shifts the emphasis.

Original:

Siyo tu mwalimu wetu mkali, bali pia ni mwenye huruma.
Emphasis: Not only is he/she our strict teacher, but also compassionate.

Reordered:

Mwalimu wetu siyo tu mkali, bali pia mwenye huruma.
Emphasis: Our teacher is not only strict, but also compassionate.

Both are fine; they just highlight different parts:

First one: “not only our strict teacher, but also compassionate”
Second one: “our teacher is not only strict, but also compassionate”

Both versions are good patterns to copy.