Learn Hardcore Swahili: Kaka alinunua begi jipya la mgongoni kwa ajili ya vitabu vyake vizito. - My brother bought a new backpack for his heavy books.

Kaka basically means “brother,” usually a male sibling of roughly your generation. In many contexts it does imply older brother, but Swahili doesn’t mark “older/younger” as strictly as some other languages unless you add words like mdogo (younger) or mkubwa (older):

kaka yangu – my brother (often older, but not necessarily)
kaka mkubwa – older brother
kaka mdogo – younger brother

In your sentence, kaka is just “(my) brother / the brother / a brother,” and Swahili can omit the possessive (yangu) if it’s clear from context whose brother it is.

How is alinunua formed, and what tense is it?

Alinunua breaks down like this:

a- = subject prefix for he/she
-li- = past tense marker (simple past)
nunua = verb root “to buy”

So alinunua = “he/she bought.”

This is the normal simple past (often called past definite). Compare:

ananunua – he/she is buying / buys (present / habitual)
amenunua – he/she has bought (present perfect, often “has just bought”)
atanunua – he/she will buy (future)

So in your sentence, it refers to a completed action in the past: “(he) bought.”

What noun class is begi, and what is its plural?

Begi (“bag”) is a loanword that’s treated as Class 5 (ji-/Ø) in the singular and Class 6 (ma-) in the plural.

Singular: begi – a bag
Plural: mabegi – bags

Knowing it’s in Class 5/6 explains the form of the adjective jipya (see the next question).

Why is it begi jipya and not begi mpya?

The adjective “new” in Swahili has the root -pya, and it changes form depending on the noun class.

For Class 5/6 (like begi / mabegi):

Class 5 singular: jipya (begi jipya) – a new bag
Class 6 plural: mapya (mabegi mapya) – new bags

So:

begi jipya – grammatically matches Class 5
begi mpya – is less standard; mpya is the Class 9/10 form and also used as a sort of “default” in casual speech, but textbook-correct agreement here is jipya.

That’s why you see begi jipya in your sentence.

What does la mgongoni literally mean, and why is la used?

La mgongoni can be broken down as:

la – the “of” linker agreeing with a Class 5 noun (begi)
mgongo – back (as a body part)
-ni – locative ending, meaning “on/at/in”

So mgongoni = “on the back,” and begi jipya la mgongoni = “a new bag of the back / for the back,” i.e. a backpack.

Why la? Because la is the associative linker for Class 5 nouns:

Class 1: wa – rafiki wa mtoto (friend of the child)
Class 5: la – begi la mgongoni (bag of/on the back)
Class 7: cha – chumba cha kulala (room for sleeping)

So la agrees with begi (Class 5).

What does kwa ajili ya do here? Could we just say kwa?

Kwa ajili ya is a fixed phrase that means “for the purpose of / for the sake of.”

kwa – by/with/at/for (very general preposition)
ajili – purpose/sake
ya – “of” agreeing with ajili (Class 9/10)

So kwa ajili ya vitabu vyake vizito literally: “for the purpose of his heavy books,” i.e. for his heavy books.

If you said only:

begi jipya la mgongoni kwa vitabu vyake vizito

this would more likely be understood as “a backpack with his heavy books” or “by means of his heavy books,” which is odd.

Kwa ajili ya specifically marks intended purpose: the bag is intended for his heavy books.

Why is it vitabu vyake vizito and not vitabu yake vizito?

Because vitabu (“books”) is Class 8 (vi-/vyi-/vy-), and both the possessive and the adjective must agree with that class.

Noun: vitabu (Class 8)
Possessive “his/her”: vyake (vi-
- -ake → vyake)
Adjective “heavy”: vizito (vi-
- -zito)

So we get:

vitabu vyake vizito – his/her heavy books

Yake (without the v-) would be correct for some other classes, e.g.:

kitabu chake – his/her book (Class 7)
nyumba yake – his/her house (Class 9/10)

But with vitabu (Class 8) you need vyake.

Does vyake mean “his” or “her”? How can you tell?

Vyake can mean “his,” “her,” or “its.” Swahili third-person singular pronouns and possessives are not gendered.

vyake = “his/her/its (Class 8 thing(s))”

You know whether it’s “his” or “her” only from context:

If you were talking about a brother, it’s natural to interpret vyake as his.
If the owner were a woman you were talking about, you’d still use vyake, but in English you’d translate it as her.

What does vizito agree with, and where does it come from?

Vizito is an adjective meaning “heavy” that agrees with vitabu (Class 8).

Root: -zito (“heavy, weighty”).

Agreement pattern:

Class 7 (singular): kizito – heavy (singular, ki-)
Class 8 (plural): vizito – heavy (plural, vi-)
Class 9 (singular): nzito – heavy (e.g. kazi nzito – a heavy/difficult job)

In your sentence:

vitabu vizito = heavy books
vizito matches vitabu in class and number.

Can the word order be vitabu vizito vyake instead of vitabu vyake vizito?

Both vitabu vyake vizito and vitabu vizito vyake are possible, but the most neutral, common order is:

Noun
Possessive
Descriptive adjective(s)

So:

vitabu vyake vizito – his heavy books (normal, neutral order)

Putting the descriptive adjective before the possessive (vitabu vizito vyake) is less common and can sound a bit more marked, sometimes giving extra emphasis to the heaviness:

more like: “those heavy books of his”

But grammatically, both orders are acceptable; Swahili allows some flexibility in adjective order, with the last element often carrying the most emphasis.