Learn Hardcore Swahili: Tabia mbaya ya kuchelewa darasani inapaswa kubadilishwa mapema. - The bad habit of being late to class should be changed early.

It is a common collocation: tabia mbaya = a bad habit / bad behavior.
Mbaya comes after the noun (unlike English, where the adjective comes before: bad habit).
Tabia is a class 9/10 noun, and mbaya is in its invariant form; it doesn’t change shape to agree with the noun.

Examples:

Ana tabia mbaya ya kusema uongo. = He/She has a bad habit of lying.
Tabia mbaya zinapaswa kuepukwa. = Bad habits should be avoided.

Why is it ya kuchelewa and not wa kuchelewa after tabia mbaya?

Ya here is a possessive/associative marker meaning of, and it must agree with the noun class of tabia.

Tabia is in noun class 9/10.
The class 9/10 possessive marker for of (singular) is ya.

So:

tabia mbaya ya kuchelewa = the bad habit of being late

If the head noun were in a different class, the marker would change, for example:

tabia zake mbaya za kuchelewa = his/her bad habits of being late
- zake / za here agree with tabia in class 10 plural.

So ya is correct because it matches tabia in class 9, not class 2 (which would take wa).

What exactly is kuchelewa? Is it a noun or a verb here?

Kuchelewa is the infinitive form of the verb chelewa (to be late).

ku- = infinitive marker
chelewa = verb root meaning to be late / to be delayed

In this sentence, kuchelewa functions like a noun (a verbal noun or gerund):

tabia mbaya ya kuchelewa darasani
= the bad habit of being late to class

So grammatically:

Form: infinitive verb.
Function: noun phrase (being late), similar to -ing forms in English (being late, smoking, lying).

Why is it darasani and not just darasa?

Darasa means class / classroom as a simple noun.

Adding -ni at the end often makes a locative form, meaning in / at / on that place.

darasa = class / classroom
darasani = in class / in the classroom / during class

So:

kuchelewa darasani = to be late to class / for class / for the lesson

Other examples of this locative -ni:

nyumba → nyumbani = at home
kanisa → kanisani = in church
shule → shuleni = at school

What does inapaswa mean, and how strong is it compared to words like lazima?

Inapaswa comes from the verb paswa, which means to be required / to be expected / to be supposed to.

inapaswa ≈ should / ought to / is supposed to / is expected to

Strength compared to other modal words:

lazima = must / have to (strong obligation)
- Tabia mbaya… lazima ibadilishwe. = The bad habit must be changed.
inapaswa = should / ought to (strong recommendation, moral or social expectation)
- … inapaswa kubadilishwa. = … should be changed.
inafaa / inastahili = can mean it is appropriate / it deserves, often softer or more evaluative.

So inapaswa is softer than lazima, but still more than just a suggestion. It implies a clear expectation or obligation.

How is inapaswa formed grammatically?

Inapaswa can be broken down like this:

i- = subject prefix for noun class 9/10 (singular)
(agreeing with tabia)
-na- = present/habitual tense marker (is / does)
paswa = verb root meaning to be required / to be supposed to

So:

i-na-paswa = it is required / it should / it is supposed to

Full structure in the sentence:

Tabia mbaya ya kuchelewa darasani (subject, class 9)
inapaswa (verb, agrees with class 9 subject)
kubadilishwa mapema (infinitive phrase, what should happen)

What does kubadilishwa mean, and how is it different from kubadilika or kubadilisha?

All three are related to the root -badil- (change), but they differ in voice and transitivity.

kubadilisha
- Form: ku- (infinitive) + badilisha (causative/active)
- Meaning: to change something / to make something different
- Example: Tunapaswa kubadilisha ratiba. = We should change the schedule.
kubadilishwa
- Form: ku- (infinitive) + badilishwa (passive of badilisha)
- Meaning: to be changed (by someone/thing)
- In the sentence: inapaswa kubadilishwa = should be changed
- It focuses on what happens to the habit, not on who changes it.
kubadilika
- Form: ku- (infinitive) + badilika (intransitive / become changed)
- Meaning: to change / to become different (by itself, or without mentioning an agent)
- Example: Tabia yake imebadilika. = His/Her behavior has changed.

In your sentence, kubadilishwa is used because:

tabia is the thing that is to be changed (passive idea: by someone).

What does mapema add here? Is it the same as haraka?

Mapema means early / soon / at an early stage.

In this sentence:

inapaswa kubadilishwa mapema
= should be changed early / as soon as possible / before it continues too long

Comparison:

mapema
- Focus: time (early, not late).
- Often implies before things get worse or before it goes on too long.
- Example: Amka mapema. = Wake up early.
haraka
- Focus: speed (quickly, fast).
- Example: Fanya kazi haraka. = Do the work quickly.

So you would not normally say kubadilishwa haraka here if you mean at an early stage; mapema is the natural adverb in this context.

Why is the word order tabia mbaya ya kuchelewa darasani and not tabia ya kuchelewa darasani mbaya like in English?

In Swahili, descriptive adjectives like mbaya usually come after the noun they describe, and they normally stay inside the noun phrase, before any longer verb-like complements.

Structure of the noun phrase:

tabia (noun, head)
mbaya (adjective, directly describing tabia)
ya kuchelewa darasani (prepositional/genitive phrase: of being late to class)

So:

tabia mbaya ya kuchelewa darasani
= literally habit bad of being-late in-class

If you say tabia ya kuchelewa darasani mbaya, it sounds unnatural and confusing, because:

mbaya has been separated from tabia by a long phrase.
Typically, you keep the main adjective close to the noun.

Correct/normal:

tabia mbaya ya kuchelewa darasani ✅

Why is it inapaswa and not zinapaswa, even though tabia can be plural?

Tabia is one of those nouns that:

Has the same form for both singular and plural (class 9/10).
Can mean habit (single) or habits (multiple), depending on context.

Agreement:

Singular tabia (one habit) → class 9 → i- as subject prefix:
- Tabia mbaya… inapaswa kubadilishwa. = This bad habit should be changed.
Plural tabia (habits) → class 10 → zi- as subject prefix:
- Tabia mbaya… zinapaswa kubadilishwa. = Bad habits should be changed.

In your sentence, inapaswa suggests that tabia mbaya is being treated as one specific habit (the habit of being late to class), not multiple different habits.

Could the sentence be rephrased more explicitly, for example with tabia hii or a clearer subject?

Yes. You can make the subject more explicit or emphatic. Some natural variants:

Adding a demonstrative:
- Tabia hii mbaya ya kuchelewa darasani inapaswa kubadilishwa mapema.
  = This bad habit of being late to class should be changed early.
Making it more general:
- Tabia mbaya za kuchelewa darasani zinapaswa kubadilishwa mapema.
  = Bad habits of being late to class should be changed early.
  (now plural: za / zinapaswa)
Using a more direct or stronger form:
- Tabia mbaya ya kuchelewa darasani lazima ibadilishwe mapema.
  = The bad habit … must be changed early.

All keep the same core idea, but adjust number (singular/plural), emphasis, and strength of obligation.