Baba alijaza dumu la maji asubuhi.

Alijaza can be split as:

• a- = subject marker for he/she or a singular person noun
• -li- = past tense marker
• jaza = verb root meaning fill

So alijaza means he filled or she filled, depending on context.

Because Baba refers to one person, and Swahili verbs agree with the noun class of the subject. A singular human subject normally takes the class 1 subject marker a-.

So:

• Baba alijaza = Father filled
• Mama alijaza = Mother filled

Even though baba is a noun, the verb still needs its subject marker.

It can mean either he filled or she filled. Swahili does not distinguish he and she in this verb form. The subject marker a- covers both.

In this sentence, Baba makes it clear that the subject is father/dad, so the meaning is he filled.

Swahili usually does not use articles like English a, an, or the.

So dumu could mean:

• a jerrycan/container
• the jerrycan/container

The exact meaning comes from context, not from an article.

Because la must agree with dumu, not with maji.

Here:

• dumu is a class 5 noun in the singular
• the associative/genitive linker for class 5 is la

So:

• dumu la maji = jerrycan/container of water or water container

If it were plural, it would change:

• madumu ya maji = water containers

So ya would be used with madumu, not with singular dumu.

La is a linking word often translated as of. It connects one noun to another.

So:

• dumu la maji = literally container of water

This pattern is very common in Swahili. The linker changes form depending on the noun class of the first noun:

• mtoto wa shule = child of school / schoolchild
• kitabu cha mwanafunzi = book of the student
• dumu la maji = container of water

Maji is a little special. It often behaves like a class 6 noun in form, but it usually means the mass noun water, not waters in the normal English sense.

For learners, the important point in this sentence is:

• maji means water
• the linker is still la because it agrees with dumu, not maji

So the phrase is still dumu la maji.

Asubuhi means morning, and in a sentence it often means in the morning or sometimes this morning, depending on context.

Swahili often uses time expressions without a preposition. So you do not need a separate word for in here.

• asubuhi = morning / in the morning

That is completely natural in Swahili.

Yes. Time expressions are fairly flexible in Swahili.

These are all possible:

• Baba alijaza dumu la maji asubuhi.
• Asubuhi, Baba alijaza dumu la maji.

The version you were given is a normal, neutral word order.

Yes. Because the verb already has a subject marker, alijaza can stand on its own if the subject is understood from context.

So:

• Alijaza dumu la maji asubuhi. = He/She filled the water container in the morning.

Adding Baba makes the subject explicit and clear.

Yes, quite similar here. The sentence follows a basic Subject–Verb–Object pattern:

• Baba = subject
• alijaza = verb
• dumu la maji = object
• asubuhi = time expression

So the structure is close to English, even though the verb itself carries more grammatical information.

The main change would be in the tense marker inside the verb.

• Baba anajaza dumu la maji asubuhi. = Father is filling / fills the water container in the morning.
• Baba atajaza dumu la maji asubuhi. = Father will fill the water container in the morning.

Compare the tense markers:

• a-li-jaza = he filled
• a-na-jaza = he is filling / he fills
• a-ta-jaza = he will fill