Learn Hardcore Swahili: Leo jioni, tutatembelea marafiki kwao. - This evening, we will visit friends at their place.

jioni hii or hii jioni – also this evening, with a slight emphasis on this.
jioni ya leo – more literally the evening of today; a bit more formal.

Jioni leo is understandable but sounds less natural; time phrases with leo usually go leo asubuhi / leo mchana / leo jioni / leo usiku in that order.

Why is there no separate word for we in the sentence?

In Swahili, the subject is usually built into the verb as a prefix, so you normally do not add a separate pronoun.

tutatembelea
- tu- = we
- -ta- = future
- -tembelea = to visit

So tutatembelea already means we will visit.
If you really want to emphasize we, you can add the pronoun:

Sisi tutatembelea marafiki kwao. – We (as opposed to others) will visit our friends.

But in neutral sentences, the pronoun (sisi) is omitted.

How is tutatembelea formed, and how would it change with other subjects or tenses?

tutatembelea is:

tu- (we) + -ta- (future) + -tembele- (visit) + -a (final vowel)

Other subjects in the future:

nitatembelea – I will visit
utatembelea – you (sg) will visit
atatembelea – he / she will visit
tutatembelea – we will visit
mutatembelea – you (pl) will visit
watatembelea – they will visit

With a different tense, for example present:

tunatembelea – we are visiting / we visit
(tu-
- -na-
  - -tembelea)

Past:

tulitembelea – we visited
(tu-
- -li-
  - -tembelea)

Why is it tutatembelea marafiki and not tutatembelea kwa marafiki?

The verb tembelea already means to visit (a person / place) and takes a direct object:

tutatembelea marafiki – we will visit (our) friends

Here marafiki is the direct object of tutatembelea.

The preposition kwa is not used to mark the object; it usually marks a location, especially someone’s place:

tuko kwa marafiki – we are at (our) friends’ place

So tutatembelea kwa marafiki sounds odd; it mixes visit with a preposition that is not needed for the object. The natural pattern is:

tutatembelea marafiki kwao / nyumbani kwao
= we will visit (our) friends at their place / at their home.

What exactly does kwao mean, and how is it different from wao?

Wao on its own means they / them (independent pronoun).

Kwao is kwa + -o and means at their place / to their place / with them, depending on context.

The pattern is:

kwangu – at my place
kwako – at your (sg) place
kwake – at his / her place
kwetu – at our place
kwenu – at your (pl) place
kwao – at their place

In the sentence tutatembelea marafiki kwao, kwao is understood as:

at their place (the friends’ home / place)

Could I say nyumbani kwao instead of kwao? Does that change the meaning?

Yes, you can say:

Leo jioni, tutatembelea marafiki nyumbani kwao.

Nyumbani kwao means at their home, while kwao is slightly broader: at their place / with them. In most everyday situations, kwao is understood as at their home anyway, so:

kwao ≈ nyumbani kwao

Adding nyumbani just makes it explicitly home.

Why don’t we say our friends (marafiki zetu) in the sentence? Is marafiki alone enough?

In Swahili, the context often makes possession obvious, so you do not always have to say our / my / their.

In tutatembelea marafiki kwao, the kwao makes it clear we are talking about their place, i.e., the place of those friends we are visiting. In a typical conversation, it is naturally understood as our friends, unless the context points to some other group.

If you want to be explicit:

Leo jioni, tutatembelea marafiki zetu kwao.
– This evening we will visit our friends at their place.

Both are grammatically correct; marafiki alone is often enough in ordinary speech.

What does marafiki tell me about number? Could rafiki also be plural?

Standard pattern:

rafiki – friend (singular)
marafiki – friends (plural)

So in this sentence marafiki clearly means friends (more than one).

In everyday speech, some people use rafiki for both singular and plural (especially in some regions), but rafiki / marafiki is the clearest and safest pattern to learn:

rafiki yangu – my friend
marafiki zangu – my friends

What exactly is the role of kwao here? Are we visiting them or their place?

Grammatically, marafiki is the object of tutatembelea:

tutatembelea marafiki – we will visit (our) friends

Then kwao adds the idea of location, literally at their place.

So the structure is:

tutatembelea (we will visit)
marafiki (the friends)
kwao (at their place)

We are visiting them, and the sentence also tells us where (at their place), not that we are visiting their house instead of them.

Where can the time expression go? Is Leo jioni, tutatembelea marafiki kwao the only correct order?

Time expressions in Swahili are quite flexible. Common options are:

Leo jioni, tutatembelea marafiki kwao.
Tutatembelea marafiki kwao leo jioni.
Leo jioni tutatembelea marafiki kwao. (without the comma in informal writing)

All of these are acceptable. Putting the time phrase at the beginning is very common and sounds natural.

How would I say This evening we are visiting friends at their place (more like an arranged plan, close to present) instead of we will visit?

Use the present/progressive marker -na-:

Leo jioni, tunatembelea marafiki kwao.

Breakdown:

tu- – we
-na- – present / progressive
-tembelea – visit

This can mean we are visiting or we are going to visit (it’s planned), similar to English We’re visiting our friends this evening.

How do I make the sentence negative: This evening we will not visit our friends at their place?

For the negative future, use the negative subject prefix plus -ta-:

Leo jioni, hatutatembelea marafiki kwao.
– This evening we will not visit (our) friends at their place.

Breakdown:

ha-tu- – we (negative)
-ta- – future
-tembelea – visit

If you want to say our friends explicitly:

Leo jioni, hatutatembelea marafiki zetu kwao.
– This evening we will not visit our friends at their place.

Is the comma after Leo jioni required in Swahili?

No, it is not strictly required. Swahili punctuation largely follows European (especially English) usage:

Leo jioni, tutatembelea marafiki kwao.
Leo jioni tutatembelea marafiki kwao.

Both are fine. The comma just clearly separates the time phrase from the rest of the sentence, but many writers omit it in informal text.