Learn Hardcore Swahili: Kanuni mpya za usafi zimetangazwa na mwalimu mkuu leo. - The new hygiene rules have been announced by the headteacher today.

The subject here is kanuni mpya za usafi (kanuni = rules).
Kanuni belongs to noun class 9/10 (N-class).
- Singular example: kanuni (a rule)
- Plural example: kanuni (rules) – same form, but the verb shows the number.

For class 9/10:

Singular subject takes the verb prefix i-
- e.g. Kanuni mpya imetangazwa. – A new rule has been announced.
Plural subject takes the verb prefix zi-
- Kanuni mpya zimetangazwa. – New rules have been announced.

Because we’re talking about rules (plural), the verb must agree and use zi-, giving zimetangazwa.

What are the parts of the verb zimetangazwa, and what does each part mean?

The verb zimetangazwa can be broken down as:

zi- – subject prefix for class 10 plural (here: kanuni = rules)
-me- – perfect tense marker (roughly “have been / has been” or completed action with present relevance)
tangaza – verb root meaning announce
-w- – passive suffix (turns “announce” into “be announced”)
-a – final vowel that closes the verb form

So zimetangazwa literally encodes:
they (class-10 things) have been announced.

Why is the passive used (zimetangazwa) instead of an active form? Could we use an active sentence here?

Yes, you can also use an active form:

Mwalimu mkuu ametangaza kanuni mpya za usafi leo.
The head teacher has announced the new hygiene rules today.

The passive version is:

Kanuni mpya za usafi zimetangazwa na mwalimu mkuu leo.
The new hygiene rules have been announced by the head teacher today.

Differences in feel:

Passive (original sentence) puts kanuni mpya za usafi (the new rules) at the front and makes them the main focus.
Active puts mwalimu mkuu (the head teacher) at the front and focuses on who did the announcing.

Both are correct; it’s mainly about which part of the sentence you want to highlight:
the rules (passive) or the teacher (active).

How can na mean by here? I thought na meant “and” or “with”.

Na is a very flexible word in Swahili. It can mean:

and – mwalimu na mwanafunzi (teacher and student)
with – ninasoma na rafiki yangu (I’m studying with my friend)
by (agent in a passive sentence) – zimetangazwa na mwalimu mkuu (have been announced *by the head teacher*)

In passive constructions, na is used to introduce the doer of the action:

Mti umeangushwa na upepo. – The tree has been knocked down by the wind.
Barua imeandikwa na mwanafunzi. – The letter has been written by the student.

So here, na mwalimu mkuu is “by the head teacher” because the verb is in the passive.

Why is the tense marker -me- used instead of -li-? What is the nuance of zimetangazwa vs zilitangazwa?

Both tenses are grammatically possible, but they don’t feel the same:

-me- = perfect (completed action, result is relevant now, often “has/have done”)
- Kanuni mpya za usafi zimetangazwa leo.
  The new hygiene rules have been announced today.
  → Focus on the new situation now (the rules are now in force / known).
-li- = simple past (completed in the past, no special link to the present)
- Kanuni mpya za usafi zilitangazwa leo.
  The new hygiene rules were announced today.
  → More of a report of a past event, less emphasis on the current state.

In everyday Swahili, -me- is very common when you talk about something that just happened and is still relevant now, which fits well with new rules announced today.

What exactly does kanuni mean, and what noun class is it in?

Kanuni generally means:

rules, regulations, principles, or guidelines

Examples:

Kanuni za shule – school rules
Kanuni za sarufi – grammar rules
Kanuni za usafi – hygiene rules / cleanliness rules

Noun class:

Kanuni belongs to class 9/10 (N-class).
Its singular and plural forms are the same: kanuni.
- You know singular vs plural from context and verb agreement:
  - Kanuni hii ni rahisi. – This rule is easy. (singular; verb uses i-)
  - Kanuni hizi ni rahisi. – These rules are easy. (plural; verb uses zi-)

Why is it mpya and not something like kipya or jipya? How do adjectives agree with kanuni?

The form of the adjective depends on the noun class of the noun it describes.

The adjective root is -pya (new).
For class 9/10 (N-class), the agreement form is mpya in both singular and plural.

So:

kanuni mpya – new rule / new rules
nguo mpya – new clothes
habari mpya – new news / new information

Forms like kipya, jipya, vipya, etc. are used with other noun classes:

kitu kipya (class 7) – a new thing
jambo jipya (class 5) – a new matter/issue
vitu vipya (class 8) – new things

Because kanuni is class 9/10, the correct adjective form is mpya.

Why do we say za usafi and not ya usafi or wa usafi?

The word za is a possessive/associative marker (often translated as of) that must agree with the noun class and number of the head noun.

The structure is:

[head noun] + [agreeing “of” word] + [following noun]

Here:

Head noun: kanuni (class 10, plural)
“of” word: za → this is the form for class 10 plural
Following noun: usafi (cleanliness / hygiene)

So:

kanuni za usafi – rules of cleanliness / hygiene rules

Other examples of class 9/10 plural with za:

nguo za watoto – children’s clothes (clothes of children)
habari za asubuhi – morning news (news of the morning)

Forms like ya and wa are used with other noun classes:

kitabu cha mwanafunzi (class 7: cha)
jina la mtoto (class 5: la)
mtu wa kijiji (class 1: wa)

So za is correct because it matches the class 10 plural noun kanuni.

What is the difference between usafi and safi?

They are related but used differently:

safi – an adjective meaning clean, pure, neat
- nyumba safi – a clean house
- mavazi safi – clean clothes
usafi – a noun meaning cleanliness, cleaning, or hygiene
- kupenda usafi – to like cleanliness
- siku ya usafi – cleaning day
- kanuni za usafi – hygiene rules / rules of cleanliness

The u- prefix often turns adjectives or other roots into abstract nouns in Swahili (class 14), e.g.:

ugonjwa (disease) from gonjwa
uzuri (beauty, goodness) from zuri (good, beautiful)

What does mwalimu mkuu literally mean, and is it always “head teacher”?

Literally:

mwalimu – teacher (class 1)
mkubwa / mkuu – big, chief, main, great

The phrase mwalimu mkuu is a set expression that normally means:

head teacher, principal, or headmaster/headmistress

More generally, mkuu is used in many titles to mean chief / head / main:

waziri mkuu – prime minister (literally “chief minister”)
mkuu wa shule – head of the school
mkuu wa kituo – station chief / person in charge of the station

So in this sentence, mwalimu mkuu is naturally understood as the head teacher (not just any “big teacher”).

Why is it mwalimu mkuu (singular) when we are talking about kanuni (rules, plural)? Shouldn’t something agree in number?

Number agreement in Swahili works within each noun phrase and between a subject and its verb, but different noun phrases don’t have to match each other in number.

Here:

Subject: Kanuni mpya za usafi (plural, class 10)
- Verb: zimetangazwa (plural zi- to agree with kanuni)
Agent phrase (introduced by na): na mwalimu mkuu
- This is one person (the head teacher), so it’s correctly singular.

So the agreement pattern is:

Kanuni (plural) → zimetangazwa (plural verb)
mwalimu mkuu (singular) → no need to change it; it just describes who did the action.

There is no rule that all nouns in the sentence must have the same number; each one is free to be singular or plural as needed.

Why is leo (today) placed at the end? Could it appear in another position?

Time expressions in Swahili, like leo (today), jana (yesterday), kesho (tomorrow), are quite flexible in position. All of these are possible and natural:

Leo kanuni mpya za usafi zimetangazwa na mwalimu mkuu.
Kanuni mpya za usafi leo zimetangazwa na mwalimu mkuu.
Kanuni mpya za usafi zimetangazwa leo na mwalimu mkuu.
Kanuni mpya za usafi zimetangazwa na mwalimu mkuu leo. ← your sentence

Differences are mainly in rhythm and slight emphasis:

Putting leo at the beginning (Leo …) can emphasize the time: “Today, …”
Putting leo near the end, like in your sentence, is very common in speech and flows naturally, with the main new information (that the rules have been announced) coming before the time.

So yes, it can appear in other positions; the meaning stays the same.

Is there any difference in meaning between kanuni mpya za usafi and “new hygiene rules” in English, or is it a direct match?

They are very close in meaning, but the Swahili structure is a bit more transparent:

kanuni – rules
mpya – new
za usafi – of cleanliness / of hygiene

Literally: “new rules of cleanliness”.

English typically compresses that to “new hygiene rules”. So:

Swahili: [rules] [new] [of hygiene]
English: [new] [hygiene] [rules]

It’s basically a direct match in content; the order and structure just follow the usual patterns of each language.