Dumu lile likiwa tupu, tutalijaza tena kabla ya jioni.

Dumu is a class 5 singular noun in Swahili. That matters because other words in the sentence have to agree with it.

In this sentence, class 5 agreement shows up as:

• lile = that (for a class 5 noun)
• li- in li-kiwa = it as the subject
• li- in tuta-li-jaza = it as the object

So if you know dumu is class 5, the rest of the sentence becomes much easier to follow.

Because lile is the demonstrative that agrees with a class 5 singular noun.

So:

• dumu lile = that container

A learner often notices that Swahili does not use one single word for that with every noun. The form changes depending on the noun class.

Likiwa can be broken down as:

• li- = subject marker for it (class 5)
• -ki- = a marker often meaning if, when, or while
• -wa = from kuwa, to be

So likiwa means roughly:

• if it is
• when it is
• while it is

In this sentence, likiwa tupu means if/when it is empty.

It can mean any of those, depending on context.

In many sentences, -ki- gives an idea like:

• if
• when
• whenever
• sometimes while

So dumu lile likiwa tupu could be understood as:

• if that container is empty
• when that container is empty

English forces you to choose more clearly, but Swahili often leaves that nuance to context.

Because ni works well for a simple present statement, such as:

• Dumu lile ni tupu = That container is empty

But in this sentence, the meaning is not just a plain statement. It is a conditional/temporal idea: if/when it is empty. For that, Swahili commonly uses kuwa in forms like likiwa.

So:

• ni tupu = simple statement
• likiwa tupu = if/when it is empty

This is a very natural question.

Tupu means empty here, and with class 5 singular, the adjective often appears with no visible prefix. So:

• dumu tupu = an empty container
• dumu lile likiwa tupu = when that container is empty

In other noun classes, you may see a clearer prefix. So the lack of an extra visible prefix here is normal.

Tutalijaza breaks down like this:

• tu- = we
• -ta- = future marker, will
• -li- = object marker, it (referring to dumu)
• -jaza = fill

So tutalijaza means:

• we will fill it

This is a very common Swahili pattern: the object can be built directly into the verb.

Because they are doing two different jobs, but both refer to the same noun, dumu.

• In likiwa, li- is the subject marker: it is
• In tutalijaza, li- is the object marker: fill it

So both point back to dumu, but one means it as the thing doing the being, and the other means it as the thing being filled.

Tena usually means again, once more, or sometimes back depending on context.

Here it gives the idea of refilling:

• tutalijaza tena = we will fill it again

Without tena, the sentence would simply say we will fill it. With tena, it suggests that the container has been filled before and will be filled another time.

Kabla ya jioni means before evening or before nightfall, depending on context.

Breakdown:

• kabla ya = before
• jioni = evening

So the phrase sets a time limit:

• before evening
• by evening in some natural English translations

Because kabla ya is the normal Swahili way to say before when it is followed by a noun.

Examples:

• kabla ya jioni = before evening
• kabla ya kazi = before work

If a verb follows, you also commonly get:

• kabla ya kujaza = before filling

So kabla ya is a very useful fixed pattern to learn.

Yes. That would also be correct and would mean roughly the same thing:

• Tutajaza dumu lile tena kabla ya jioni = We will fill that container again before evening

The difference is mainly style and focus:

• tutalijaza = we will fill it
  This is more compact and uses an object marker.
• tutajaza dumu lile = we will fill that container
  This repeats the full noun.

Once the container is already known, Swahili very often prefers the shorter verb with the object marker.

The comma is helpful because the first part is an introductory if/when-clause:

• Dumu lile likiwa tupu, ...

Then the main clause follows:

• ... tutalijaza tena kabla ya jioni.

So the comma works much like it would in English after If the container is empty, ... It makes the sentence easier to read, even though spoken Swahili relies more on pause and intonation than on punctuation.