Learn Hardcore Swahili: Hofu ya mtoto ilipungua alipomwona mtu mzima akitabasamu. - The child’s fear decreased when she saw an adult smiling.

Because the possessive marker agrees with the noun that is possessed, not with the possessor. The possessed noun hofu is class 9/10, whose possessive concord is ya. Hence hofu ya mtoto (“the child’s fear”). If the possessed noun were class 1, you’d use wa, e.g., mtoto wa mwalimu (“the teacher’s child”).

How is ilipungua put together, and why does it start with i-?

Breakdown: i-li-pungua.

i-: subject agreement for a class 9 noun (here, hofu).
-li-: past tense.
-pungua: verb stem “decrease, lessen” (intransitive). So it means “it decreased,” with “it” referring to hofu.

What does each part of alipomwona do?

Breakdown: a-li-po-mw-ona.

a-: class 1 subject (“he/she,” here referring to mtoto).
-li-: past tense.
-po-: temporal “when” marker forming a subordinate clause.
mw-: class 1 object marker (“him/her,” referring to the adult).
-ona: “see.” Together: “when he/she saw him/her.”

What exactly does the -po- in alipomwona express?

It turns the verb into a time-setting clause: “when (he/she) saw…”. Swahili uses -po- in this construction for “when/at the time that.”

What is the mw- in alipomwona, and is it required?

mw- is the class 1 object marker (“him/her”). It becomes mw- before a vowel-initial stem like -ona (otherwise it appears as m-).
It’s not strictly required when the object noun follows. Without it you get alipoona mtu mzima. Including the object marker usually signals that the object is specific/known or emphasized.

So what nuance difference is there between alipomwona mtu mzima and alipoona mtu mzima?

alipomwona mtu mzima: “when (the child) saw the adult” (more specific/identifiable adult).
alipoona mtu mzima: “when (the child) saw an adult” (introducing a new/indefinite adult). Both are grammatical; context guides the choice.

Can I write alipomuona instead of alipomwona?

Yes. The class 1 object marker appears as:

m- before consonants: anampenda (“he/she loves him/her”).
mw- before vowel-initial stems: anamwona (“he/she sees him/her”).
mu- is also common: anamuona; likewise, you’ll see both alipomwona and alipomuona. All are acceptable; it’s largely phonology and orthographic preference.

What does akitabasamu mean here?

It’s a-ki-tabasamu:

a-: class 1 subject (“he/she”).
-ki-: simultaneous/continuative marker, roughly “while/when (doing).”
tabasamu: “smile” (verb). So akitabasamu means “while smiling,” describing an action happening at the same time as the seeing.

Who is the one smiling—the child or the adult?

The adult. akitabasamu directly follows mtu mzima, so it modifies that noun; its subject prefix a- agrees with class 1 (mtu). Both mtoto and mtu are class 1, so the prefix alone could match either; positioning makes it clear. To make it absolutely explicit, use a relative clause like mtu mzima ambaye alikuwa akitabasamu or mtu mzima aliyekuwa akitabasamu.

Could I use a relative like anayetabasamu instead of akitabasamu?

Yes. Options include:

mtu mzima anayetabasamu: “the adult who is smiling” (present/ongoing description).
mtu mzima ambaye alikuwa akitabasamu or mtu mzima aliyekuwa akitabasamu: “the adult who was smiling” (explicitly past-simultaneous).
mtu mzima akitabasamu is lighter and focuses on the action occurring at that moment.

Does mtu mzima literally mean “whole person”?

Literally mzima means “whole/complete/healthy,” but the idiomatic pairing mtu mzima means “adult, grown-up.” For “whole person,” you’d typically rephrase (e.g., mtu kamili). The adjective mzima agrees with class 1 (m-); with other classes it changes, e.g., tunda zima (“a whole fruit,” class 5).

What’s the difference between kupungua and kupunguza in this context?

kupungua: intransitive “to decrease/lessen (by itself).” Hence hofu ilipungua (“the fear decreased”).
kupunguza: transitive “to reduce (something).” E.g., tabasamu la mtu mzima lilipunguza hofu ya mtoto (“the adult’s smile reduced the child’s fear”).
Passive: kupunguzwa (“to be reduced”): hofu ya mtoto ilipunguzwa na tabasamu.

If I make any of the participants plural, what agreement changes?

Plural children as subject of the “when” clause: Hofu ya watoto ilipungua walipomwona mtu mzima akitabasamu. Main verb still agrees with hofu (class 9: i-), but the “when” clause subject becomes class 2 plural: wa-li-po-… → walipomwona.
Plural adults as object/actor: … walipowaona watu wazima wakitabasamu. Object marker wa- (class 2 plural) and wakitabasamu to agree with watu.

Where does akitabasamu go in the sentence? Can it be moved?

It should follow the noun it modifies: mtu mzima akitabasamu. Moving it elsewhere risks ambiguity or oddness. If you need more flexibility, use a relative clause: mtu mzima ambaye alikuwa akitabasamu.

Is a comma required before the alipo- clause?

No. Swahili doesn’t require a comma before alipo- clauses. Writers may add one for readability in long sentences, but it’s optional.

Is -po- always temporal “when”?

In this verbal construction, -po- can mark definite time (“when”) or definite location (“where”), depending on context. Here it’s clearly temporal (“when he/she saw…”). With verbs that imply place, -po- can be locative, e.g., alipofika (“when/where he arrived”).

What’s the nuance difference between tabasamu and cheka if I used akicheka instead?

tabasamu = “smile”; akitabasamu = “while smiling” (quiet, gentle).
cheka = “laugh”; akicheka = “while laughing” (audible, stronger). Using akicheka changes the scene’s feel.