Stuli hii imo jikoni, lakini kiti kikubwa kiko sebuleni.

They are related but not identical.

• stuli usually means stool, often a simpler seat, sometimes without a back
• kiti usually means chair or more generally seat

So the sentence contrasts this stool with the big chair. In real life, usage can overlap a bit depending on context, but they are not usually exact synonyms.

In normal Swahili word order, the noun usually comes first, and words that describe or point to it come after it.

So:

• stuli hii = this stool
• kiti hiki = this chair

That is different from English, where this comes before the noun.

Because stuli is treated as a class 9 noun in the singular.

In Swahili, nouns belong to noun classes, and words connected to the noun must agree with that class. For class 9 singular nouns, the demonstrative is hii.

So:

• stuli hii = this stool

The same class also uses i- in verb agreement, which is why you see imo.

Both words contain agreement with the noun.

• stuli is class 9 singular, so it takes i-
• kiti is class 7 singular, so it takes ki-

That gives:

• i-mo
• ki-ko

These are locative forms, used for saying where something is.

A simple way to think of them is:

• imo = it is in / it is inside
• kiko = it is there / it is located

In everyday Swahili, speakers may not always keep a strong difference between -ko and -mo, but broadly:

• -ko is more general location
• -mo often suggests being inside something

So Stuli hii imo jikoni has a natural inside the kitchen feeling.

Not as a separate English-style word.

In location sentences, Swahili often uses forms like:

• iko
• kiko
• imo
• ziko

These already include the idea of is / are located.

So kiko sebuleni means something like:

• it is in the living room
• it is located in the living room

The subject agreement is built into the form itself.

The ending -ni is a very common locative ending. It often means in, at, or to a place.

So:

• jikoni = in the kitchen
• sebuleni = in the living room

This is one of the main ways Swahili expresses location.

Because adjectives in Swahili usually have to agree with the noun class.

The noun kiti is class 7, and class 7 often uses the prefix ki-.
The adjective stem is -kubwa, meaning big.

So:

• kiti kikubwa = big chair

Compare:

• kiti kikubwa = singular
• viti vikubwa = plural

This agreement is very important in Swahili.

Yes. lakini means but or however.

It connects two clauses:

• Stuli hii imo jikoni
• lakini
• kiti kikubwa kiko sebuleni

So the structure is very similar to English:

• This stool is in the kitchen, but the big chair is in the living room.

Swahili does not normally use articles like English the and a/an.

So:

• kiti kikubwa can mean a big chair or the big chair
• the exact meaning depends on context

English requires an article, but Swahili usually does not.

With many loanwords like stuli, the noun itself may stay the same, but the agreement words change.

Singular:

• stuli hii imo jikoni = this stool is in the kitchen

Plural:

• stuli hizi zimo jikoni = these stools are in the kitchen

Notice the changes:

• hii → hizi
• imo → zimo

So number is often shown by agreement, not just by changing the noun itself.

Yes. iko is also very natural.

A useful rough guide is:

• iko = general location
• imo = in / inside

So both can work, especially with a place like jikoni.
Using imo can make the location feel a bit more inside that place, but in everyday speech many speakers would also say iko.

You would make both the adjective and the demonstrative agree with kiti.

So:

• kiti hiki kikubwa = this big chair

Breakdown:

• kiti = chair
• hiki = this, for class 7 nouns
• kikubwa = big, agreeing with class 7

That shows a very common Swahili pattern: multiple words around the noun all agree with its noun class.