Ukirudi kutoka sokoni, usisahau kuniletea ndimu.

Ukirudi is made of:

• u- = you (singular)
• -ki- = a marker often meaning if or when
• -rudi = return / come back

So ukirudi means if you return or when you come back.

In this sentence, English would usually translate it more naturally as when you come back.

It can mean either, depending on context.

In Swahili, -ki- often introduces a clause like:

• if/when you...
• if/when he...
• if/when they...

So ukirudi kutoka sokoni could literally be understood as if/when you return from the market.

In everyday English, when is usually the most natural translation here, because the speaker expects the person to come back.

Soko means market.

The ending -ni is a very common locative ending in Swahili. It often gives the sense of:

• in
• at
• to

So:

• soko = market
• sokoni = at the market / in the market / to the market

After kutoka (from), sokoni gives the idea from the market.

Kutoka means to come from, from, or out of.

Here it connects with sokoni:

• kutoka sokoni = from the market

So the first part is:

• Ukirudi kutoka sokoni = When you come back from the market

Usisahau is a negative command addressed to one person.

It breaks down like this:

• u- = you (singular)
• si- = negative marker
• sahau = forget

So usisahau means don't forget.

This is the normal way to make a negative command to one person in Swahili.
If you were speaking to more than one person, you would usually say msisahau = don't forget (you all).

Kuniletea can be broken down as:

• ku- = to (infinitive marker)
• -ni- = me
• letea = bring to / bring for

So kuniletea means to bring to me or more naturally to bring me.

That means:

• usisahau kuniletea ndimu = don't forget to bring me lemons/limes

This is a very good question.

• kuleta = to bring
• kuletea = to bring to/for someone

The extra -e-/-ea part adds the idea of a recipient or beneficiary.

So:

• kuleta ndimu = to bring lemons/limes
• kuniletea ndimu = to bring me lemons/limes

In other words, -lea / -tea here helps express bring to me rather than just bring in a more general sense.

Ndimu is commonly used for lime or lemon, depending on region and context. In many cases, the same form can serve as both singular and plural.

So ndimu may mean:

• a lime / a lemon
• limes / lemons

The exact number is often understood from context.
In this sentence, English often translates it as lemons or some lemons/limes, because that sounds natural after bring me.

Swahili often places the time/condition clause first and the main instruction after it.

So the structure is:

• Ukirudi kutoka sokoni = When you come back from the market
• usisahau kuniletea ndimu = don't forget to bring me lemons/limes

This order is very natural in Swahili, just like English can naturally say:

• When you come back from the market, don't forget to bring me lemons.

Yes. If you want to sound more explicitly polite, you can add tafadhali = please.

For example:

• Ukirudi kutoka sokoni, tafadhali usisahau kuniletea ndimu.

That means:

• When you come back from the market, please don't forget to bring me lemons/limes.

Even without tafadhali, the original sentence is normal and natural. Adding it just makes the request more overtly polite.