Mvua ikianza, tutarudi nyumbani.

ikianza can be broken into:

• i- = the subject prefix agreeing with mvua
• -ki- = a marker meaning if/when
• -anza = the verb stem begin/start

So ikianza literally means something like if/when it begins.

In this sentence, the thing that begins is mvua (rain), so the sense is if/when the rain starts.

Because mvua belongs to a noun class that takes i- as its subject marker.

Swahili uses noun classes instead of only natural gender or fixed articles like English. Verbs have to agree with the noun they go with.

So:

• mvua = rain
• subject agreement for this noun = i-

That is why you get:

• mvua inaanza = the rain is starting
• mvua ikianza = if/when the rain starts

Even though mvua does not look like it begins with i-, the verb still agrees with it using i-.

It can mean if, when, or whenever, depending on context.

In a sentence like Mvua ikianza, tutarudi nyumbani, English could translate it as:

• If it starts raining, we will go home
• When it starts raining, we will go home

Swahili -ki- often covers both ideas. English usually forces you to choose one, but Swahili can leave it a bit more open.

A helpful way to think of -ki- is:

• a condition: if
• a time link: when

The context tells you which feels more natural.

Because mvua inaanza is a full main clause meaning the rain is starting.

But here the speaker wants a subordinate clause meaning if/when the rain starts. For that, Swahili uses the -ki- form:

• mvua inaanza = the rain is starting
• mvua ikianza = if/when the rain starts

So ikianza is not just a normal present tense form. It is a special dependent form used to connect the idea to the main clause.

tutarudi breaks down as:

• tu- = we
• -ta- = future tense
• -rudi = return/go back

So tutarudi means we will return or we will go back.

In this sentence:

• Mvua ikianza, tutarudi nyumbani
• If/when the rain starts, we will go back home

Because the sentence is talking about what will happen after the condition is met.

The structure is:

• Mvua ikianza = if/when the rain starts
• tutarudi nyumbani = we will go home

English does something similar:

• If it rains, we will go home

Even though English often uses present tense in the if clause, the result clause is future. Swahili works similarly here.

nyumbani means at home, home, or to home, depending on context.

It comes from nyumba (house/home) plus the locative ending -ni, which gives a place meaning.

So:

• nyumba = house
• nyumbani = at home / home

In this sentence, tutarudi nyumbani means we will return home or we will go back home.

Because Swahili often does not need a separate preposition where English uses to.

The locative form nyumbani already gives the idea of location or destination. So:

• tunarudi nyumbani = we are going back home
• literally not word-for-word we are returning to home, but that is the meaning

This is very normal in Swahili.

Yes. In natural English, people often say if it starts raining, while Swahili here literally uses rain as the subject:

• mvua = rain
• ikianza = if/when it begins

So the Swahili structure is closer to if the rain starts, but the natural English translation is often if it starts raining.

Both express the same idea.

In practice, mvua is usually treated as a mass noun, like rain in English.

You normally do not think of it as one rain / two rains in everyday use. What matters most for the learner is that it takes its noun-class agreement, such as i- on the verb.

So the key point is not really singular vs. plural in the English sense, but:

• mvua has its own agreement pattern
• that is why you see i- in ikianza

That would change the meaning.

• tutarudi = we will return
• turudi = let us return / we should return (subjunctive or jussive-type meaning)

So:

• Mvua ikianza, tutarudi nyumbani = If/when it starts raining, we will go home
• Mvua ikianza, turudi nyumbani = more like If/when it starts raining, let’s go home or we should go home

The original sentence uses the normal future statement, not a suggestion or command.

The given order is the most natural and clear:

• Mvua ikianza, tutarudi nyumbani

This puts the condition first, then the result.

You may sometimes hear different ordering in speech or writing for emphasis, but for learners, this pattern is the safest:

1. condition clause with -ki-
2. main clause

So a good model to remember is:

• X ikitokea, Y itafanyika
• If/when X happens, Y will happen

A very useful pattern is:

• [subject] + [subject prefix] + -ki- + verb stem, [main clause]

Examples:

• Mgeni akifika, tutaanza. = When/if the guest arrives, we will begin.
• Chakula kikiisha, tutapika tena. = If/when the food runs out, we will cook again.
• Mwalimu akija, tutanyamaza. = When/if the teacher comes, we will be quiet.

From your sentence:

• Mvua ikianza, tutarudi nyumbani.

So the big grammar point is the -ki- form for if/when clauses.