Learn Hardcore Swahili: Sasa mimi ninaosha sahani peke yangu kwa sababu wengine wanasoma. - Now I am washing the plates by myself because the others are studying.

In Swahili, the subject marker on the verb (here ni- for “I”) is obligatory, but the independent pronoun (mimi) is optional and used for emphasis or contrast.

ni- in ninaosha already shows that the subject is “I”.
mimi adds emphasis, like saying “Me, I am washing the dishes…” or “I’m the one washing…”.

You can absolutely say:

Sasa ninaosha sahani peke yangu kwa sababu wengine wanasoma.

This is fully correct and very natural.
Using mimi just stresses that it’s you (not someone else) doing the washing.

How is the verb ninaosha formed, and what tense is it?

ninaosha can be broken down like this:

ni- = subject marker for “I”
-na- = present tense marker (often called the “present continuous”)
-osha = verb root meaning “wash”

So ninaosha literally means “I am washing” (an action happening now, or around now).

Other examples:

ninala / ninalia (depending on dialect) – I am eating
unasoma – you are reading/studying
wanacheza – they are playing

Could I just say naosha sahani instead of ninaosha sahani?

In everyday spoken Swahili, many people do shorten nina- to na-, so you will often hear:

Naosha sahani = “I’m washing the dishes.”

However:

In formal / standard Swahili (e.g., for exams or careful writing), ninaosha is considered the correct full form.
naosha is very common in speech, but learners are usually taught ninaosha first.

So:

Informally: Naosha sahani – widely used, understood.
Formally/standard: Ninaosha sahani – recommended.

Does sasa always mean “now,” or can it also mean “so / well” like in English?

sasa primarily means “now” in a time sense:

Sasa ninaosha sahani. – Now I’m washing the dishes.

But in conversation it can also function as a discourse marker, a bit like “so”, “well”, or “okay then” in English, especially at the beginning of a sentence:

Sasa, tufanye nini? – So, what shall we do?
Sasa, twende. – Okay then, let’s go.

In your sentence, sasa is most naturally understood as “now,” but in context it can also feel like “so now / and now” depending on how it’s said.

Is sahani singular or plural? Why isn’t there a special plural ending?

sahani can be both singular and plural, depending on context. It’s a loanword (originally from Arabic) and belongs to a noun class where singular and plural look the same.

So:

sahani = a plate / the plate
sahani = plates / the plates

You know whether it’s singular or plural from:

context, or
agreements (adjectives, numbers, etc.), e.g.:
- sahani moja – one plate
- sahani mbili – two plates

What exactly does peke yangu mean, and why do we use yangu there?

peke yangu means “by myself / on my own / alone (me)”.

peke = alone / only / by oneself
yangu = “my / mine” (possessive for first-person singular, agreeing with a noun like mimi or an implied “self”)

So peke yangu literally feels like “my own alone-ness” → “by myself / alone”.

Other persons:

peke yako – by yourself (you, singular)
peke yake – by himself / herself
peke yetu – by ourselves
peke yenu – by yourselves (you, plural)
peke yao – by themselves

In your sentence:

ninaosha sahani peke yangu = “I am washing the dishes by myself.”

What’s the difference between peke yangu and mwenyewe, as in ninaosha sahani mwenyewe?

Both can translate as “by myself”, but they have slightly different flavors:

peke yangu literally emphasizes being alone / with no one else.
mwenyewe emphasizes doing it oneself / personally, often like English “myself, personally”.

Often they overlap:

Ninaosha sahani peke yangu. – I’m washing the dishes alone (no one is helping).
Ninaosha sahani mwenyewe. – I’m washing the dishes myself (I’m the one doing it, not someone else).

You can also combine them for strong emphasis:

Ninaosha sahani peke yangu mwenyewe. – I’m washing the dishes all by myself (absolutely no one else involved).

Why is it kwa sababu as two words? Could it also be written together like kwasababu?

Standard, correct writing is kwa sababu as two words:

kwa – a preposition (“by / with / because of / for” depending on context)
sababu – “reason / cause”

So kwa sababu literally means “for (this) reason / because”.

You may sometimes see kwasababu in informal texts (social media, texting), but in proper writing and learning materials, you should use:

kwa sababu – because.

What does wengine mean exactly? Does it mean “others” or “the others”? Do I need to say watu wengine?

wengine is a plural noun meaning “others / other people” (from the word -ngine, “other/different”).

In many contexts, wengine alone is enough to mean “the others” (people you and the listener know about from context):

wengine wanasoma – the others are studying / other people are studying.

You can say watu wengine (“other people”), but that’s usually when you are introducing the idea of “some people” in general, not specific known “others.”

So in your sentence, wengine naturally reads as “the others” (the other people in the situation you’re talking about).

Why is it wanasoma and not wamesoma? What’s the difference between these two forms?

Both are present-time forms, but with different aspects:

wanasoma
- wa- = they
- -na- = present tense
- -soma = read/study
  → “they are studying / they are reading (now / these days)”
wamesoma
- wa- = they
- -me- = perfect aspect
- -soma
  → “they have studied / they have read” (the action is completed, with result now)

In your sentence:

wengine wanasoma = the others are currently studying (their ongoing activity now).
wengine wamesoma would mean the others have already studied (they’re done studying).

Is the word order Sasa mimi ninaosha sahani peke yangu kwa sababu wengine wanasoma fixed, or can I move things around?

Swahili word order is relatively flexible, especially for emphasis, as long as the verb structure stays correct. Your sentence is perfectly natural, but you could also say, for example:

Sasa ninaosha sahani peke yangu kwa sababu wengine wanasoma.
(Drop mimi; still natural.)
Sasa ninaosha sahani kwa sababu wengine wanasoma, peke yangu.
(Puts peke yangu at the end for emphasis.)
Sasa mimi, kwa sababu wengine wanasoma, ninaosha sahani peke yangu.
(More contrastive, like: “Now me, because the others are studying, I’m washing the dishes by myself.”)

You generally keep:

Subject (often optional as a full pronoun)
Verb (with subject marker, tense, root)
Object
Adverbs/phrases like peke yangu, kwa sababu…
but you can shuffle for emphasis and style.

Could I use something else instead of kwa sababu to mean “because”?

Yes, Swahili has several common ways to say “because”:

kwa sababu – very common and neutral
- Sina muda kwa sababu ninasoma. – I don’t have time because I’m studying.
kwa kuwa – slightly more formal/literary
- Sina muda kwa kuwa ninasoma.
maana – often conversational, sometimes like “because / since / as”
- Sina muda maana ninasoma. – I don’t have time because I’m studying.

All three could be used in your sentence with small stylistic differences:

… peke yangu kwa sababu wengine wanasoma.
… peke yangu kwa kuwa wengine wanasoma.
… peke yangu maana wengine wanasoma.