Learn Hardcore Swahili: Wageni watakao kuja ukumbini leo jioni watafurahi. - The guests who will come to the hall this evening will be happy.

Putting them together as Wageni watakuja ukumbini leo jioni watafurahi would be understood as something like “The guests will come to the hall this evening and they will be happy,” not specifically “the guests who will come … will be happy.”

Using watakao makes a restrictive relative clause:

Wageni watakao kuja ukumbini leo jioni – The guests *who will come to the hall this evening*
… watafurahi. – … will be happy.

So watakao signals that “will come to the hall this evening” is describing which guests you mean.

Sometimes I see watakaokuja written as one word. Is watakao kuja with a space correct, and what’s the difference?

Both forms are used and understood:

Wageni watakao kuja ukumbini leo jioni…
Wageni watakaokuja ukumbini leo jioni…

They mean the same thing: “the guests who will come to the hall this evening …”

Points to note:

Writing it together (watakaokuja) treats the whole thing as one verb complex, and is common in grammars and more formal writing.
Writing it separately (watakao kuja) treats kuja more like an infinitive “to come”. This spelling also appears in real usage and is widely understood.

As a learner, if you want to be very “textbook-safe”, you can prefer the joined form watakaokuja, but the sentence as given is also acceptable in everyday usage.

Could I also say Wageni ambao watakuja ukumbini leo jioni watafurahi? How is that different from watakao kuja?

Yes, you can say:

Wageni ambao watakuja ukumbini leo jioni watafurahi.

Here ambao is a separate relative pronoun meaning “who/that”.

Comparison:

Wageni watakao kuja… – uses a conjugated relative form (watakao)
Wageni ambao watakuja… – uses ambao plus a normal finite verb (watakuja)

Both are correct and natural. Differences:

watakao kuja / watakaokuja is shorter and very common in speech and writing.
ambao watakuja can feel a bit heavier, sometimes clearer for learners or in very formal styles.

In most contexts, they are interchangeable in meaning.

What does ukumbini literally mean, and why not just ukumbi?

Ukumbi = hall
-ni is a locative suffix meaning in/at/on.

So:

ukumbini = in the hall / at the hall

This -ni ending is very common with places:

nyumba → nyumbani – at home / in the house
kanisa → kanisani – in/at church
darasa → darasani – in the classroom

You could also say:

katika ukumbi or kwenye ukumbi = in the hall

But ukumbini is the simplest and most idiomatic here.

What exactly does leo jioni mean? Could I just say jioni or leo?

Leo jioni literally is “today evening”, and corresponds to “this evening” in English.

Options and nuances:

leo jioni – this evening (today); quite specific.
jioni – in the evening; could mean today, or just “in the evening” generally, depending on context.
leo – today (any time during the day).

You can move the time phrase around:

Leo jioni wageni watakao kuja ukumbini watafurahi.
Wageni watakao kuja ukumbini watafurahi leo jioni.

All are fine; Swahili is flexible with time expressions, though they often come near the verb or at the beginning.

How do wageni, watakao, and watafurahi agree with each other?

Wageni (guests) is the plural of mgeni and belongs to noun class 2 (wa-/wa-), used for people.

Agreement works like this:

Subject noun: wageni (class 2, plural humans)
Subject prefix for class 2: wa-
So the verbs and relative form also take wa-:
- watakao – who will (they)
  - wa- (they, class 2) + future-relative stuff (as explained earlier)
- watafurahi – they will be happy / they will rejoice
  - wa- (they) + -ta- (will) + furahi (be happy)

If it were only one guest:

Mgeni atakayekuja ukumbini leo jioni atafurahi.
- mgeni – singular guest (class 1)
- a- – class 1 subject prefix: atakayekuja, atafurahi

Is furahi a verb? Why is it watafurahi and not something like watakuwa na furaha?

Yes, -furahi is a verb meaning “to be happy / to be glad / to rejoice.”

So:

watafurahi = they will be happy / they will rejoice.

In Swahili, many states that are adjectives in English are expressed by verbs:

amechoka – he/she is tired
nimefurahi – I am happy / I am glad
utafurahi – you will be happy

You can also say:

Watakuwa na furaha. – They will have happiness / They will be happy.

Nuance:

watafurahi often suggests a reaction or feeling of joy about something (more event-like).
watakuwa na furaha sounds a bit more like a state of possessing happiness.

In the given sentence, watafurahi is very natural and idiomatic.

How would the sentence look in the past tense: “The guests who came to the hall this evening were happy”?

One natural version is:

Wageni waliokuja ukumbini leo jioni walifurahi.

Breakdown:

waliokuja – who came
- wa- – they (class 2)
- -li- – past tense
- -o- – relative ending for plural humans
- kuja – come
walifurahi – they were happy / they rejoiced
- wa- – they
- -li- – past
- furahi – be happy

Compare to the original future version:

watakao kuja (who will come) → waliokuja (who came)
- future -ta-
  - -ka- becomes past -li- in the relative form.

How would I say “The guests who will come to the hall this evening will not be happy”?

You just negate the main verb:

Wageni watakao kuja ukumbini leo jioni hawatafurahi.

Explanation:

watafurahi – they will be happy
hawatafurahi – they will not be happy

Formation of hawatafurahi:

Negative prefix for “they” in the future: hawa-
Future marker -ta-
Verb stem furahi

→ hawa-ta-furahi → written together as hawatafurahi.

The rest of the sentence stays the same.

Do I need a comma anywhere in this Swahili sentence, like in some English relative clauses?

No comma is needed in Swahili here:

Wageni watakao kuja ukumbini leo jioni watafurahi.

This is a restrictive relative clause (“the guests who will come …”), and in Swahili it is normally written without a comma.

In speech, you might make a slight pause before watafurahi, but you don’t normally show that pause with a comma in standard Swahili spelling.