Learn Hardcore Swahili: Jana usiku, mwizi alikamatwa sokoni na polisi. - Last night, a thief was arrested at the market by the police.

a- = subject prefix for 3rd person singular (he/she/it, or a class 1 noun like mwizi)
-li- = past tense marker (simple past)
kamat- = verb root from kukamata (to arrest/catch)
-w- = passive marker
-a = final vowel

So alikamatwa literally means he/she/it was arrested/caught, or more naturally here: (the) thief was arrested.

Why is jana usiku at the beginning of the sentence? Could it go elsewhere?

Jana usiku means last night and is an adverbial time phrase. In Swahili:

Time expressions often come at the beginning to set the scene, especially in narratives.
You can also say:
- Mwizi alikamatwa sokoni na polisi jana usiku.
- Mwizi alikamatwa jana usiku sokoni na polisi.

All are grammatically correct; the difference is just emphasis and style. Putting jana usiku first emphasizes when it happened.

What is the difference between jana usiku and usiku wa jana?

Both can mean last night, but there is a nuance:

jana usiku: very common, neutral way to say last night.
usiku wa jana: more literally the night of yesterday; also correct and used, sometimes sounds a bit more formal or descriptive.

In this sentence, Jana usiku, mwizi alikamatwa… is the most natural everyday choice.

Why is it sokoni and not soko?

Sokoni is soko (market) with the locative suffix -ni.

soko = market (as a noun)
sokoni = at the market / in the market / to the market

Swahili uses -ni to mark location:

nyumba (house) → nyumbani (at home)
shule (school) → shuleni (at school)
kanisa (church) → kanisani (at church)

So alikamatwa sokoni = was arrested at the market.

Does na here mean and or by?

In this sentence, na has an instrumental/agent meaning, not just and:

na can mean:
- and (connecting words/phrases):
  - mama na baba = mother and father
- with:
  - ninaenda na rafiki yangu = I’m going with my friend
- by (agent in a passive sentence):
  - alikamatwa na polisi = he/she was arrested by the police

Here na polisi means by the police (the doer of the action in the passive).

Is polisi singular or plural? Does it mean a policeman or the police?

Polisi can function both ways, depending on context:

As a mass/collective noun: the police (the force as a whole)
- Polisi walifika haraka. = The police arrived quickly.
As an individual: a policeman/police officer
- In many dialects, askari is more common for police officer, but polisi can be used.

In alikamatwa sokoni na polisi, the natural translation is was arrested at the market by the police (collective).

Why is there no word for a or the before mwizi?

Swahili does not use articles like English a/an or the. The noun mwizi can mean:

a thief
the thief
just thief as a general category, depending on context.

Context decides whether you translate it as a or the:

First time mentioning: usually a thief
Known/previously mentioned: usually the thief

In this example, English would typically say: Last night, a thief was arrested…

Why is the verb alikamatwa singular when polisi (police) seems plural?

In Swahili, the verb agrees with the subject, not the agent in the na phrase.

The subject of the sentence is mwizi (thief), which is a class 1 (singular) noun, so:

Subject: mwizi → subject prefix a-
Verb: alikamatwa

Even though polisi can be understood as a group (plural idea), it is not the grammatical subject. It appears in the na phrase as the agent of the passive, so it does not control verb agreement.

What would the active version of this sentence look like?

The passive sentence:

Jana usiku, mwizi alikamatwa sokoni na polisi.
= Last night, a thief was arrested at the market by the police.

An active equivalent:

Jana usiku, polisi walimkamata mwizi sokoni.

Breakdown:

polisi = police (subject)
wa- = subject prefix for they (class 2 / plural humans)
-li- = past tense
-m- = object marker for him/her (mwizi)
-kamata = arrest/catch

So literally: Last night, the police arrested him/her (the thief) at the market.

How does mwizi fit into the noun class system, and does that affect the sentence?

Mwizi belongs to the M-WA noun class (class 1/2 for people):

Singular: mwizi (thief) – class 1
Plural: wezi (thieves) – class 2

This affects:

Subject agreement on the verb
- Singular: mwizi alikamatwa (a thief was arrested)
- Plural: wezi walikamatwa (thieves were arrested)
Adjective and pronoun agreement, if used:
- mwizi mmoja (one thief), wezi wawili (two thieves), etc.

In the given sentence, the a- in alikamatwa agrees with singular mwizi.

Could you replace mwizi with another noun, and what would change?

Yes; the noun class affects verb agreement. For example:

Jana usiku, mwanafunzi alikamatwa sokoni na polisi.
(Last night, a student was arrested at the market by the police.)
- mwanafunzi is also class 1 → a- prefix: alikamatwa.
Jana usiku, wanafunzi walikamatwa sokoni na polisi.
(Last night, students were arrested at the market by the police.)
- wanafunzi is class 2 (plural) → wa- prefix: walikamatwa.

So you must change the verb prefix (a-, wa-, etc.) to match the subject’s noun class and number.

Is the comma after jana usiku necessary in Swahili?

The comma is not strictly required for grammatical reasons, but it is common and helpful:

Jana usiku, mwizi alikamatwa sokoni na polisi.
Jana usiku mwizi alikamatwa sokoni na polisi.

Both are acceptable. The comma just makes the pause clearer, separating the time phrase (jana usiku) from the main clause, much like in English.

Could jana usiku be replaced with another time expression, and would anything else in the sentence have to change?

Yes, you can swap in other time expressions without changing the rest of the sentence. For example:

Leo asubuhi, mwizi alikamatwa sokoni na polisi.
= This morning, a thief was arrested at the market by the police.
Juzi, mwizi alikamatwa sokoni na polisi.
= The day before yesterday, a thief was arrested at the market by the police.
Wiki iliyopita, mwizi alikamatwa sokoni na polisi.
= Last week, a thief was arrested at the market by the police.

Only the time phrase changes; the structure of the rest of the sentence stays the same.