Learn Hardcore Swahili: Wakati ulikuwa ukifua nguo bafuni, mtoto alikuwa akicheza sebuleni. - While you were washing clothes in the bathroom, the child was playing in the living room.

Together: ulikuwa ukifua = you were (in the process of) washing.
Swahili often uses kuwa + verb with -ki- to express past continuous (was/were doing).

What exactly is the difference between ulikuwa ukifua and ulifua?

Both are past tense, but the aspect (how the action unfolds in time) is different:

Ulifua nguo
- Simple past: “You washed clothes.”
- Focuses on the action as a completed event.
Ulikuwa ukifua nguo
- Past continuous/progressive: “You were washing clothes.”
- Emphasizes that the action was ongoing at a specific time or while something else was happening.

In the sentence:

Wakati ulikuwa ukifua nguo bafuni, mtoto alikuwa akicheza sebuleni.

the continuous form (ulikuwa ukifua, alikuwa akicheza) nicely matches the meaning “while you were washing…, the child was playing…”, i.e. two actions happening at the same time in the past.

Why do we also have mtoto alikuwa akicheza instead of just mtoto alicheza?

It’s the same pattern as ulikuwa ukifua:

mtoto = the child
a- = he/she (3rd person singular subject marker, or class 1 noun subject marker)
-li- = past tense
kuwa = to be
a- = he/she
-ki- = ongoing/incomplete action
-cheza = play

So mtoto alikuwa akicheza = “the child was playing”, not just “the child played”.

Using past continuous for both verbs makes it clear that:

your washing and
the child’s playing

were simultaneous, both in progress at that time.

If you said:

Wakati ulifua nguo bafuni, mtoto alicheza sebuleni.

it would be understandable, but it sounds more like two completed events in sequence, not necessarily overlapping in time.

What is the role of -ki- in ukifua and akicheza?

The -ki- in ukifua and akicheza is an incomplete / simultaneous action marker. It often corresponds to:

“while doing X”
“when doing X”
or simply the progressive (be doing) when combined with kuwa in the past.

Structures like:

kuwa + (subject) + -ki- + verb

are very common to express ongoing actions, especially in the past:

Nilikuwa nikisoma. = I was reading.
Walikuwa wakifanya kazi. = They were working.
Ulikuwa ukifua. = You were washing.
Mtoto alikuwa akicheza. = The child was playing.

So, -ki- contributes the idea of “in the middle of / in the process of doing something”.

Why do we use wakati at the beginning? Can we say the same thing without it?

Wakati literally means “time”, and in this kind of sentence it works like English “when / while” introducing a time clause:

Wakati ulikuwa ukifua nguo bafuni, …
When/While you were washing clothes in the bathroom, …

You can express a similar idea without wakati by using -ki- or -po directly on the verb, for example:

Ulipokuwa ukifua nguo bafuni, mtoto alikuwa akicheza sebuleni.
= When you were washing clothes in the bathroom, the child was playing in the living room.

Here ulipokuwa = u- (you) + -li- (past) + -po- (when/where) + kuwa (to be).

So, two common patterns:

Wakati + [normal past clause]
- Wakati ulikuwa ukifua …, mtoto alikuwa akicheza …
[verb with -po-] + [other clause]
- Ulipokuwa ukifua …, mtoto alikuwa akicheza …

Both are correct; wakati + clause is very transparent for learners, because it matches English “when/while …” quite closely.

Can I change the word order and put the child’s action first: Mtoto alikuwa akicheza sebuleni wakati ulikuwa ukifua nguo bafuni?

Yes. Swahili allows you to swap the order of these two clauses without changing the basic meaning:

Wakati ulikuwa ukifua nguo bafuni, mtoto alikuwa akicheza sebuleni.
Mtoto alikuwa akicheza sebuleni wakati ulikuwa ukifua nguo bafuni.

Both roughly mean:
“While you were washing clothes in the bathroom, the child was playing in the living room.”

Small nuance:

Putting wakati… first makes the time frame more prominent:
“As for the time when you were washing… (here’s what the child was doing)”.
Putting the mtoto-clause first emphasizes what the child was doing, then explains when it was happening.

Grammatically, both are fine.

What do bafuni and sebuleni mean exactly, and what does the -ni ending do?

The -ni ending is a locative suffix, often meaning “in / at / on [place]”.

bafu = bathroom
bafuni = in the bathroom
sebule = living room / sitting room
sebuleni = in the living room

So:

nguo bafuni = clothes (being washed) in the bathroom
mtoto alikuwa akicheza sebuleni = the child was playing in the living room

This -ni locative is very common:

nyumba → nyumbani = at home
shule → shuleni = at school
kanisa → kanisani = at church

In many cases, you don’t need a separate preposition like “in”; -ni does that job.

Is nguo singular or plural here, and what noun class is it?

Nguo belongs mostly to noun class 9/10, where singular and plural often look the same.

nguo (one item of clothing)
nguo (clothes, several items)

So context tells you whether nguo means “a garment” or “clothes” (plural).
In this sentence, ulikuwa ukifua nguo is naturally understood as “you were washing clothes” (plural), because that’s what people typically do: wash a batch of clothes, not just one item.

Where is the word “you” in Wakati ulikuwa ukifua nguo bafuni…? I don’t see a separate pronoun.

In Swahili, the subject is usually encoded inside the verb as a prefix, so separate pronouns are often not needed.

For “you (singular)”, the subject marker is u-.

In ulikuwa ukifua:

u-
- -li-
  - kuwa = ulikuwa = you were
u-
- -ki-
  - fua = ukifua = (you) while washing / (you) in the process of washing

So the “you” is present twice, but as subject markers:

First in ulikuwa
Then in ukifua

If you really want to emphasize you, you can add the independent pronoun:

Wewe ulikuwa ukifua nguo bafuni…
= YOU were washing clothes in the bathroom… (contrastive/emphatic).

But normally ulikuwa already clearly means “you were”.

How do we know if mtoto means “the child” or “a child”?

Swahili does not have articles like English “a/an” or “the”. A bare noun like mtoto can mean:

“a child” (indefinite)
“the child” (definite)

The difference is inferred from context, not from a word like “the”.

In your sentence:

Wakati ulikuwa ukifua nguo bafuni, mtoto alikuwa akicheza sebuleni.

a natural translation would be:

“While you were washing clothes in the bathroom, the child was playing in the living room.”

because it usually refers to a specific, known child in that situation (your child, the child in the house, etc.). But technically, in another context, you could also translate it as “a child was playing …” if you’re introducing that child for the first time.

Could I say Wakati ulifua nguo bafuni, mtoto alicheza sebuleni instead? How would that change the meaning?

You can say:

Wakati ulifua nguo bafuni, mtoto alicheza sebuleni.

This is grammatically correct, but the aspect is different:

ulikuwa ukifua / alikuwa akicheza = were washing / was playing (ongoing)
ulifua / alicheza = washed / played (simple, completed past)

So:

Wakati ulikuwa ukifua nguo bafuni, mtoto alikuwa akicheza sebuleni.
= While you were in the middle of washing clothes, the child was in the middle of playing in the living room. (two simultaneous ongoing actions)
Wakati ulifua nguo bafuni, mtoto alicheza sebuleni.
= When you washed clothes in the bathroom, the child played in the living room.
(more like two whole events: at the time you washed, he played; less focus on the “in-progress” nature)

Both are understandable, but the original sentence matches the English past continuous nuance more closely.