Mama alinunua nepi nyingi na chuchu mbili kabla ya mtoto kuzaliwa.

Because noun class in Swahili is not determined only by the first letters of a word. Mama is an animate singular noun, so it usually takes class 1 agreement, including the subject marker a- on the verb.

So:

• mama alinunua = mother/mom bought
• not a plural ma- noun in this sentence

In other words, the ma- at the beginning of mama is just part of the word, not a plural prefix here.

Alinunua can be divided like this:

• a- = he/she
• -li- = past tense
• -nunua = buy

So alinunua means he/she bought. Since the subject is mama, it means Mother/Mom bought.

Swahili does not normally use articles like English the and a/an. A noun such as mama or mtoto can mean mother / the mother or child / the child, depending on context.

So:

• mama can mean mother, the mother, or mom
• mtoto can mean a child, the child, or the baby

The context tells you which meaning is intended.

In Swahili, modifiers usually follow the noun.

So you get:

• nepi nyingi = many diapers
• chuchu mbili = two pacifiers/nipples

This is normal Swahili word order:

• noun first
• adjective/number after it

They agree with the noun class of nepi and chuchu, which are treated here as class 9/10 nouns.

That is why you see:

• nyingi = many for this noun class
• mbili = two for this noun class

Swahili adjectives and numbers often change form to match the noun they describe. So you cannot just use one single form for every noun.

Many class 9/10 nouns in Swahili have the same form in singular and plural. That includes many loanwords as well.

So:

• nepi can be singular or plural depending on context
• chuchu can also stay the same in form

The words around them help show number:

• nyingi shows that nepi is plural here
• mbili shows that there are two chuchu

Here, na means and.

It joins the two objects:

• nepi nyingi
• chuchu mbili

So:

• nepi nyingi na chuchu mbili = many diapers and two pacifiers/nipples

In other sentences, na can also mean with, so you always have to look at the context.

Kabla ya means before.

It is a fixed expression:

• kabla ya
  • noun or noun-like phrase

In this sentence:

• kabla ya mtoto kuzaliwa = before the child being born / more naturally in English, before the child was born

The ya is part of the normal structure after kabla in this kind of phrase.

Because kuzaa means to give birth, while kuzaliwa means to be born.

That difference matters:

• the mother gives birth
• the baby is born

Since the sentence is talking about the child, Swahili uses kuzaliwa, not kuzaa.

Ku- is the infinitive marker. It is the equivalent of English to in forms like to buy, to be born, to eat, and so on.

So:

• zaliwa = be born
• kuzaliwa = to be born / being born

In this sentence, kuzaliwa works like a verbal noun after kabla ya.

Yes. That is another very common way to express before the child is/was born.

The two patterns are different in structure:

• kabla ya mtoto kuzaliwa
• kabla mtoto hajazaliwa

The second one uses a full verb form and is often very natural in everyday speech. The sentence you were given uses an infinitive-style construction.

Because Swahili does not always need an object marker when the object is stated clearly after the verb.

So:

• Mama alinunua nepi nyingi... is perfectly normal

The objects are already named:

• nepi nyingi
• chuchu mbili

Object markers are often used for emphasis, clarity, or when the object has already been mentioned, but they are not required here.

Literally, mtoto means child. But in this context, it is very naturally understood as baby, because the sentence talks about the time before birth.

So although the basic word is child, English would often translate it more naturally as baby here.

Yes. The sentence follows a very normal pattern:

• subject: Mama
• verb: alinunua
• objects: nepi nyingi na chuchu mbili
• time phrase: kabla ya mtoto kuzaliwa

So the overall order is basically: Subject + Verb + Object + Time expression

That is a very common and natural Swahili sentence pattern.