Mama amesema dua ya asubuhi humtuliza mtoto.

Amesema is built from:

• a- = he/she
• -me- = perfect
• -sema = say

So amesema often means has said or said with some present relevance.

By contrast, alisema uses -li-, the simple past marker, and is more like said in a finished past sense.

So in this sentence, Mama amesema... suggests that what the mother said is still relevant now.

Swahili often leaves out kwamba (that) after verbs like say, know, or think.

So:

• Mama amesema dua ya asubuhi humtuliza mtoto.

is natural and means:

• Mother said that morning prayer calms the child.

You could also say:

• Mama amesema kwamba dua ya asubuhi humtuliza mtoto.

That version is a little more explicit, but both are correct.

Literally, it means prayer of morning:

• dua = prayer, supplication
• asubuhi = morning
• ya = a linking word meaning of, agreeing with dua

So natural English is morning prayer or prayer in the morning.

Ya is the possessive/genitive linker used to connect nouns, often translated as of.

Here it links:

• dua
  • asubuhi

to make:

• dua ya asubuhi = morning prayer / prayer of the morning

The form of this linker changes depending on the noun class of the first noun. Since dua takes the class that uses ya, that is the correct form here.

Humtuliza can be broken down like this:

• hu- = habitual / general truth
• m- = him/her (object marker for a singular animate noun)
• -tuliza = calm, soothe

So humtuliza means something like:

• it usually calms him/her
• it calms him/her
• it has a calming effect on him/her

In this sentence, the him/her refers to mtoto.

Hu- is a habitual or generalizing marker. It is often used for things that happen regularly, characteristically, or as a general truth.

So:

• dua ya asubuhi humtuliza mtoto

suggests that morning prayer tends to calm the child, or generally calms the child.

If you used inamtuliza, that would be more like a regular present form, and depending on context it could sound more immediate or less general.

So hu- fits well when talking about a repeated or typical effect.

The m- is the object marker for him/her, referring to mtoto.

So:

• humtuliza = it calms him/her

Since mtoto does not specify male or female, m- also does not specify gender.

This is very common in Swahili.

The object marker inside the verb can appear together with the full noun:

• humtuliza mtoto

This can make the sentence clearer, and with specific animate objects it is especially natural.

So the structure is a bit like:

• it calms him/her, the child

In natural English we usually would not repeat like that, but in Swahili it is normal.

The subject is dua ya asubuhi.

So the second clause works like this:

• dua ya asubuhi = subject
• humtuliza = verb
• mtoto = object

That means the morning prayer is what calms the child.

Meanwhile, Mama is only the subject of amesema in the first part of the sentence.

It can be translated in different ways depending on context:

• mother
• mom
• mum

Swahili mama is the normal word for mother, but in real use it can also work like a respectful title for a woman.

Here, because it is at the beginning of the sentence, it is capitalized automatically. That does not necessarily mean it is a proper name.

Swahili does not have articles like English a/an/the.

So nouns like:

• mama
• dua
• mtoto

appear without articles.

Whether you translate them as a or the in English depends on context. For example:

• mtoto could be a child or the child
• dua ya asubuhi could be a morning prayer or the morning prayer

In this sentence, context will decide which English version sounds best.

Yes. The basic order here is very normal.

Main clause:

• Mama amesema = Mother said

Reported clause:

• dua ya asubuhi humtuliza mtoto
  subject + verb + object

So the second clause follows the common Swahili pattern:

• Subject – Verb – Object

That makes this sentence a good example of standard Swahili clause structure.