Usipoifunga zipu ya koti lako, utahisi baridi asubuhi.

It means if you do not fasten it or if you don't zip it up.

It can be broken down like this:

u- = you (singular)
-si- = not
-po- = a conditional/time marker that gives the sense of if/when in this kind of negative form
-i- = it, referring to zipu
-fung- = close / fasten
-a = final vowel

So usipoifunga literally gives the idea if you do not fasten it.

The -i- is an object marker. It stands for zipu, which belongs to noun class 9, and the class 9 object marker is -i-.

So the verb is not just if you don’t fasten, but if you don’t fasten it.

In Swahili, this kind of object marker is often used when the object is specific or already clear from context. Since the sentence is talking about a particular zipper, the marker is very natural here.

It is often natural to include it here, but in many contexts Swahili can also omit the object marker.

So a learner may hear both:

Usipoifunga zipu ya koti lako...
and
Usipofunga zipu ya koti lako...

The version with -i- sounds more clearly tied to that specific zipper. It is a good form to learn.

Because the agreement is happening with two different nouns.

ya agrees with zipu.
lako agrees with koti.

So:

zipu ya koti lako = the zipper of your coat

More literally:

zipu = zipper
ya = of, agreeing with zipu
koti lako = your coat

This is very common in Swahili: each modifier agrees with the noun it belongs to.

Because koti is being treated here as a noun that takes class 5 agreement in the singular. For that class, your becomes lako.

So:

koti lako = your coat

A native English speaker often expects one general word for your, but in Swahili possessives change according to noun class.

Utahisi means you will feel.

It breaks down as:

u- = you (singular)
-ta- = future marker, will
-hisi = feel / sense

So utahisi baridi means you will feel cold.

Because baridi can function like cold / coldness, and Swahili often expresses this idea with the verb -hisi, meaning feel.

So:

utahisi baridi = you will feel cold

This is a very natural way to say it. English and Swahili do not always package physical sensations in exactly the same way.

Asubuhi means in the morning or simply morning.

Swahili often uses time words directly, without adding a preposition like in. So:

asubuhi = in the morning

That is completely normal Swahili word order.

Yes. The sentence has a conditional structure:

Usipoifunga zipu ya koti lako = If you don’t zip up your coat
utahisi baridi asubuhi = you will feel cold in the morning

A useful thing to notice is that Swahili does not need a separate word exactly like English if here. The idea of if you don’t is already built into usipoifunga.

It is singular you.

So this sentence is speaking to one person:

Usipoifunga... utahisi... = If you don’t fasten it, you will feel cold

If you were talking to more than one person, the subject markers would change, for example:

Msipoifunga ... mtahisi ...

So this sentence is addressed to one person.