Mwanasayansi huyo alifurahi kuona watoto wakiuliza maswali mengi baada ya somo.

In Swahili, demonstratives like this and that usually come after the noun, not before it.

So:

• mwanasayansi huyo = that scientist
• literally, it is more like scientist that

Also, huyo agrees with the noun class of mwanasayansi, which is the singular class for people.

Yes, here huyo means that. More specifically, it is the demonstrative used for a singular person noun in this noun class.

Swahili has several demonstratives depending on distance and noun class, so huyo is not a one-size-fits-all word for that. It is the form that matches mwanasayansi.

In this sentence, mwanasayansi huyo means that scientist or the scientist in question.

Alifurahi can be broken down like this:

• a- = subject marker for he/she or a singular person noun
• -li- = past tense
• -furahi = be happy / be pleased

So alifurahi means he/she was happy or became happy/pleased, depending on context.

Because the subject mwanasayansi huyo is already stated, Swahili does not need a separate word for he or she.

It can mean either he was happy or she was happy.

Swahili does not mark gender in this verb form. The subject marker a- is used for a singular person regardless of whether the person is male or female.

So the gender has to come from context, not from the verb itself.

Kuona is the infinitive form of the verb see, so it means to see.

After a verb like alifurahi (was happy), Swahili often uses an infinitive to express what someone was happy to do or experience.

So:

• alifurahi kuona... = was happy to see...

This works much like English was happy to see.

This is a very common learner question.

Wakiuliza uses -ki-, which often shows an action happening at the same time as another action, or an action viewed as ongoing in a subordinate way.

So:

• watoto wakiuliza = children asking / children while asking
• in smoother English here: the children asking questions

After a verb of perception like kuona (to see), this kind of form is very natural for describing what someone saw happening.

So:

• alifurahi kuona watoto wakiuliza maswali mengi
  = the scientist was happy to see the children asking many questions

If you used wanauliza, that would sound more like a full independent clause: the children are asking. The -ki- form fits better with seeing someone doing something.

Yes:

• wa- = subject marker for they (here, watoto)
• -ki- = while / as / in the process of
• -uliza = ask

So wakiuliza literally has the sense of while they are asking or as they ask.

In this sentence, the best natural translation is simply asking.

In Swahili, adjectives usually come after the noun.

So:

• maswali mengi = many questions
• literally: questions many

This is normal Swahili word order.

Because adjectives in Swahili must agree with the noun class of the noun they describe.

Here:

• swali = question
• maswali = questions

Maswali is a plural noun in class 6, so the adjective -ingi (many) must take the class 6 form:

• mengi

That is why:

• maswali mengi = many questions

not maswali mingi.

Baada ya is a very common expression meaning after.

So:

• baada ya somo = after the lesson / after class

The ya is part of the connective structure used after baada. You can think of baada ya as a set phrase meaning after.

Examples:

• baada ya chakula = after food / after the meal
• baada ya kazi = after work
• baada ya somo = after the lesson

Swahili does not have articles like a, an, and the.

That means:

• watoto can mean children or the children
• somo can mean a lesson, the lesson, or lesson, depending on context

When translating into English, you choose a/an/the based on the situation and what sounds natural.

So in this sentence:

• watoto is naturally understood as the children
• somo is naturally understood as the lesson

Yes. The sentence follows very normal Swahili patterns.

A simplified structure is:

• Mwanasayansi huyo = subject
• alifurahi = verb
• kuona watoto wakiuliza maswali mengi = what the scientist was happy to see
• baada ya somo = time phrase

Also notice these two common Swahili patterns:

• modifiers follow nouns: mwanasayansi huyo, maswali mengi
• the verb carries subject and tense information: alifurahi

So the sentence is a good example of standard, natural Swahili grammar.