Learn Hardcore Swahili: Usije ukasahau kofia yako; jua linawaka sana leo. - Don’t end up forgetting your hat; the sun is shining strongly today.

In Swahili, usije uka- + verb is an idiomatic cautionary pattern meaning “be careful not to (end up) … / lest you ….” Literally it’s “don’t come and then forget,” but the sense is “don’t end up forgetting.” It’s softer and more warning-like than a blunt negative command.

How is Usije formed morphologically?

u- = you (singular) subject prefix
-si- = negative
verb stem of kuja (come) in the subjunctive is irregular: -je (normally it would be -e)
So u-si-je → usije = “don’t come,” which in this pattern means “don’t (come to) … / lest you ….”

What does the -ka- in ukasahau do?

-ka- is the consecutive/sequential marker. After a warning or imperative, it often marks the undesirable consequence: u-ka-sahau ≈ “and (then) you forget / end up forgetting.” It doesn’t mark past tense here; it’s about sequence/result.

Could I just say Usisahau kofia yako instead? What’s the nuance difference?

Yes.

Usisahau kofia yako = plain negative command “Don’t forget your hat.”
Usije ukasahau kofia yako = gentler, cautionary, “Make sure you don’t end up forgetting your hat,” implying a real risk.

How would I say it to more than one person?

Use plural subject prefixes:

Msije mkasahau kofia zenu; jua linawaka sana leo.
Here, msije (you all, don’t come), mkasahau (you all then forget), and zenu (your, plural, for class 10 plural kofia).

Why is it kofia yako and not kofia wako?

Because kofia is a class 9 noun. Possessives agree with noun class: class 9 takes y- on the possessive, giving yako (your, singular). Wako is used with class 1 and some class 3 nouns (e.g., mtu wako, mti wako).

Can I add an object marker to emphasize the hat, like “Don’t end up forgetting it, your hat”?

Yes. You can resume the object with an object marker:

Usije ukaisahau kofia yako.
Here -i- is the class 9 object marker referring to kofia: u-ka-i-sahau.

What exactly does linawaka mean with jua?

Kuwaka means “to be alight/burning/blazing; to be on (lights).” With jua, linawaka means “the sun is blazing/very hot,” stronger than just “shining.” If you want mere light, you can say jua linaangaza (“the sun is giving light”).

How is jua linawaka built?

jua = sun (class 5)
li- = class 5 subject prefix
-na- = present tense marker
-waka = verb root “burn/blaze”
So li-na-waka → linawaka = “is blazing.”

Where should sana and leo go? Are other orders okay?

Most natural: Jua linawaka sana leo or Leo jua linawaka sana.
Putting sana right after the verb phrase is standard. Jua linawaka leo sana is less common/stylistically marked.

Could I say Jua ni kali sana leo instead of jua linawaka sana leo?

Yes. Jua ni kali sana leo = “The sun is very intense/fierce today.”

linawaka highlights blazing/heat as an action/state.
kali is an adjective meaning “fierce/intense,” a very common way to talk about strong sun.

What if I want to make the reason explicit rather than using a semicolon?

You can use a conjunction:

Usije ukasahau kofia yako kwa sababu jua linawaka sana leo. (…because…)
Usije ukasahau kofia yako; maana jua linawaka sana leo. (…since/because…)
A full stop also works: two separate sentences.

Is kuja always the verb used in this caution pattern?

Yes, for this idiomatic warning it’s typically usi-/msi- + je (from kuja) followed by uka-/mka-. Other movement verbs like kuenda don’t replace kuja in this function. You can add an introductory angalia (“watch out”): Angalia usije ukasahau…

How would I say “Don’t end up forgetting to bring/wear your hat”?

Bring: Usije ukasahau kuleta kofia yako.
Wear: Usije ukasahau kuvaa kofia yako.
Same cautionary frame, with an infinitive (kuleta/kuvaa) after ukasahau.

Is adding tafadhali (“please”) okay here?

Yes. Tafadhali usije ukasahau kofia yako; jua linawaka sana leo. It makes the request more polite while keeping the same cautionary nuance.