Learn Hardcore Swahili: Mwalimu alisahihisha mistari niliyoandika jana na kunionyesha kosa nililolifanya. - The teacher corrected the lines that I wrote yesterday and showed me the mistake that I made.

a- = subject marker for he / she (class 1, used with mwalimu “teacher”)
-li- = past tense marker
sahihish- = verb stem meaning “correct” (from -sahihisha)
-a = final vowel (almost all Swahili verbs end in -a in the infinitive and finite forms)

So alisahihisha literally means “he/she did-correct (in the past)”, which we translate simply as “he/she corrected.”
Because mwalimu is right before it, we understand it as “the teacher corrected …”.

Why is it mistari and not mstari here?

mstari means “a line” (singular), and mistari means “lines” (plural).

Singular: mstari = a line
Plural: mistari = lines

The noun mstari/mistari belongs to the m-/mi- noun class (class 3/4):

class 3 (singular): m- → mstari
class 4 (plural): mi- → mistari

In the sentence, the teacher is correcting several lines, so the plural mistari is used:
Mwalimu alisahihisha mistari… = The teacher corrected the lines…

What exactly does niliyoandika mean, and how is it constructed?

niliyoandika means roughly “that I wrote” and introduces a relative clause describing mistari.

Breakdown:

ni- = subject marker “I”
-li- = past tense
-yo- = relative marker agreeing with mistari (class 4)
andika = verb stem “write”
(final -a is part of the stem -andika in this analysis)

So mistari niliyoandika jana means:

mistari = the lines
niliyoandika = that I wrote
jana = yesterday

Together: “the lines that I wrote yesterday.”
The whole relative clause niliyoandika jana immediately follows the noun it describes (mistari), just like English “the lines that I wrote yesterday.”

Why is the relative marker -yo- used in niliyoandika, but -lo- is used in nililolifanya?

The choice of -yo- vs -lo- comes from noun classes:

mistari is class 4 (mi-), and its relative marker is -yo-.
kosa is class 5, and its relative marker is -lo-.

So:

mistari niliyoandika
- -yo- matches mistari (class 4) → “the lines that I wrote”
kosa nililolifanya
- -lo- matches kosa (class 5) → “the mistake that I made”

In general, different noun classes use different -o-–type relative markers, for example:

Class 1 (mtu): -ye- → mtu aliyenisaidia = the person who helped me
Class 4 (mistari): -yo- → mistari niliyoandika
Class 5 (kosa): -lo- → kosa ulilolifanya (the mistake you made)
Class 7 (kitu): -cho- → kitu nilichokiona (the thing that I saw)

So -yo- and -lo- are just the relative equivalents of “that/which” tied to different noun classes.

Do we need a word like ambayo (“which/that”) in mistari niliyoandika jana or kosa nililolifanya?

No, we don’t need a separate word like ambayo here, because the relative meaning “that/which” is already built into the verb via -yo- and -lo-.

You have two basic strategies in Swahili:

Use the verb with a relative marker (-o- form):
- mistari niliyoandika jana
  = the lines that I wrote yesterday
- kosa nililolifanya
  = the mistake that I made
Or use a separate relative pronoun (ambayo/ambalo etc.) with a normal verb:
- mistari ambayo niliandika jana
- kosa ambalo nilifanya

Notes:

You normally choose one system or the other, not both.
So mistari ambayo niliyoandika sounds redundant and unnatural.
The -o- on the verb (like niliyoandika) is very common and feels slightly more compact.
The ambayo/ambalo forms are also correct; they can feel a bit more formal or explicit, especially in writing or when the clause is long.

Why is jana placed after niliyoandika? Could it go somewhere else?

In mistari niliyoandika jana, jana is right after niliyoandika, so it naturally attaches to “I wrote”, giving:

mistari niliyoandika jana = the lines that I wrote yesterday.

That suggests:

I wrote the lines yesterday;
the teacher corrected them (not necessarily yesterday).

You can move jana, but the focus changes:

Jana mwalimu alisahihisha mistari niliyoandika na kunionyesha…
→ Emphasizes when the teacher corrected them: Yesterday the teacher corrected the lines I had written…
Mwalimu jana alisahihisha mistari niliyoandika…
→ Still tends to attach jana to alisahihisha (the correcting).
Mistari niliyoandika jana (original position)
→ Very clearly links jana to niliyoandika (the writing).

So the current position makes it most natural to understand jana as “yesterday (I wrote them)”, not “yesterday the teacher corrected them.”

What does na kunionyesha literally mean, and why is there no subject or tense marker on kunionyesha?

na kunionyesha literally breaks down as:

na = and
ku- = infinitive marker “to” (or non-finite “‑ing” form)
-ni- = object marker “me”
onyesha = “show” (verb stem)
(final -a is part of the normal verb shape)

So na kunionyesha = “and (to) show me …”

There is no subject marker (like a-) and no tense marker (like -li-) because this verb is in the infinitive form (kuonyesha) with an object marker attached (ni- → kunionyesha).

Swahili often uses:

[finite verb] … na ku‑[verb] …

to link two actions done by the same subject:

Mwalimu alisahihisha mistari … na kunionyesha kosa …
= The teacher corrected the lines … and (he/she) showed me the mistake …

The tense and subject from alisahihisha are understood to carry over to kunionyesha.

Could we say na akanionyesha kosa instead of na kunionyesha kosa? What’s the difference?

Yes, you can say:

Mwalimu alisahihisha mistari niliyoandika jana na akanionyesha kosa nililolifanya.

Meaning: still “The teacher corrected the lines … and (then) showed me the mistake I had made.”

Difference in feel:

na kunionyesha
- Second action is in the infinitive.
- Feels more like a simple listing of two related actions: he corrected … and (he) showed me ….
- Very common in explanations, instructions, more neutral style.
na akanionyesha
- Second verb is finite: a- (he/she) + -ka- (sequential past) + -ni- (me) + root.
- Feels a bit more narrative, like “and then he showed me …”, emphasizing sequence in a story.

Both are grammatical. For everyday neutral sentences, na kunionyesha is very natural; in storytelling, na akanionyesha (or just kisha akanionyesha) is also very common.

What is the difference between kunionyesha and using kuonyesha mimi for “to show me”?

Both express “to show me”, but they use different ways of marking the object “me”:

kunionyesha
- ku- = infinitive marker
- -ni- = object marker “me”
- onyesha = “show” → compact form: “to show me”
kuonyesha mimi
- kuonyesha = “to show”
- mimi = full pronoun “me” → literally “to show me”, with extra emphasis on mimi.

In normal Swahili, you almost always prefer the object marker inside the verb:

kunionyesha kosa = to show me the mistake

You might use kuonyesha mimi:

for emphasis, e.g. Alitaka kuonyesha mimi, si mtu mwingine. = He wanted to show me, not someone else.
or in very careful / formal speech.

So in this sentence, kunionyesha is the natural, standard choice.

How is nililolifanya formed, and why are there two li parts in it?

nililolifanya corresponds roughly to “that I did (it)”, referring back to kosa.

Breakdown:

ni- = subject marker “I”
-li- = past tense
-lo- = relative marker for kosa (class 5)
-li- = object marker agreeing with kosa (class 5)
fanya = verb stem “do” / “make”
-a = final vowel

So literally:

ni‑li‑lo‑li‑fanya
I – past – which – it – did

Glossed more naturally: “the mistake that I made”.

The first -li- is tense.
The second -li- is an object marker referring back to kosa.

Could we drop that object marker and just say kosa nililofanya instead of kosa nililolifanya?

You will see both, but the pattern in Swahili strongly favors including the object marker when the head noun is the direct object inside a relative clause.

So:

kosa nililolifanya
- ni-li-lo-li-fanya
- very natural Standard Swahili: “the mistake that I made (it)”
kosa nililofanya
- ni-li-lo-fanya
- omits the object marker li.
- You may hear or see this, but to many speakers it sounds a bit less natural or more bookish/foreign-influenced.

Compare other common patterns:

chakula nilichokila
(you’ll often see it as nilichokila = ni-li-cho-ki-la; with OM ki-)
vitu alivyoviiba = the things that he stole (with OM vi-)

For a learner, the safest and most idiomatic choice is:

kosa nililolifanya
vitu alivyoviiba
kitu nilichokiona, etc.

So in this sentence, nililolifanya is the form you should copy.

Why is kosa singular when mistari is plural? Does it mean there was only one mistake?

Yes. mistari is plural (lines), but kosa is singular (a mistake).

The sentence implies:

The teacher corrected many lines (mistari),
but pointed out one particular mistake (kosa) that you made in those lines.

If there were several mistakes, you would normally use the plural:

makosa = mistakes (class 6 plural of kosa)
e.g. … na kunionyesha makosa niliyoyafanya.
(and showed me the mistakes that I had made.)

So the singular kosa focuses on one specific error.

If the verb already shows the subject (with a- in alisahihisha), why do we also need mwalimu? Could we just say Alisahihisha mistari…?

In Swahili, the subject marker on the verb is obligatory, but the full noun (mwalimu) is optional when context is clear.

Alisahihisha mistari niliyoandika jana…
= He/She corrected the lines I wrote yesterday…

This is a complete sentence. The a- in alisahihisha already means “he/she”.

We add mwalimu when we want to specify who:

Mwalimu alisahihisha mistari…
= The teacher corrected the lines…

So:

Verb subject marker (a-) = he/she (or some class‑1 noun from context)
Noun (mwalimu) = tells you exactly who that “he/she” is

In natural speech and writing, speakers often omit the subject noun after it’s been mentioned, because the verb markers are enough to keep track of who is doing what.