Learn Hardcore Hausa: Ke kin sani yau babu aiki? - Did you feminine know there is no work today?

Without ke, Kin sani yau babu aiki? is still grammatically correct and means the same thing, just less emphatic.
With ke, the speaker is highlighting you (maybe contrasting you with others who don’t know).

Why is you expressed twice: Ke kin sani? Aren’t ke and kin both “you”?

Yes, both refer to “you (singular, female)”, but they are different types of pronouns:

ke = independent (emphatic / topic) pronoun.
kin = subject marker (2nd person singular feminine, perfective/completive).

So structurally:

Ke (you, topic)
kin (you, subject marker)
sani (know)

This kind of doubling is normal in Hausa when you want to emphasize the subject:

Ni na zo. – Me, I came.
Kai ka gani. – You (male), you saw it.

Here: Ke kin sani. – You (female), you know.

How do I say the same thing to a man instead of a woman?

For a male listener, you change both the independent pronoun and the subject marker:

Kai ka sani yau babu aiki?
You (male), you know there’s no work today?

or, less emphatic (no independent pronoun):

Ka sani yau babu aiki?
Do you (male) know there’s no work today?

So:

Female: Ke kin sani …
Male: Kai ka sani …

Why is this a question if there’s no question word like “what”, “do”, or “shin”?

Yes–no questions in Hausa are usually formed just by intonation, not by adding a question particle.

Statement: Ke kin sani yau babu aiki. (falling intonation)
Question: Ke kin sani yau babu aiki? (rising/final questioning intonation)

On the page/in writing, the question mark shows this, but in speech it’s mainly the intonation that turns it into a question.

You can use shin to make a yes–no question more explicit or formal:

Shin kin sani yau babu aiki?

but it’s by no means required in everyday speech.

What exactly does kin mean in kin sani?

Kin is the 2nd person singular feminine subject marker in the perfective/completive aspect.

Roughly:

na sani – I know / I knew
ka sani – you (m.sg) know / knew
kin sani – you (f.sg) know / knew
ya sani – he knows / knew
ta sani – she knows / knew

The “perfective/completive” aspect in Hausa often covers what English expresses as:

present state (you know), or
completed action (you found out / you realized),

depending on context.

So kin sani can be understood as “you (already) know”.

What is sani here? Is it a verb or a noun?

Sani is a bit special:

It is both the finite verb “to know” in many common forms (e.g. na sani, kin sani)
and also the verbal noun “knowledge” (e.g. yana da sani sosai – he has a lot of knowledge).

In this sentence, sani is functioning as the main verb:

kin sani ≈ you know / you have knowledge (of this fact)

You can also see sani taking a clause after it, often with cewa (that):

Kin sani cewa yau babu aiki. – You know that there is no work today.

In everyday speech, cewa is often dropped, as in your sentence.

Why is yau (“today”) in the middle? Could I move it?

Yau is an adverb of time and Hausa is fairly flexible with its placement. Common options:

Ke kin sani yau babu aiki?
Ke kin sani cewa yau babu aiki?
Ke kin sani babu aiki yau? (less common, but possible in context)

The most neutral and common positions are:

Immediately after the verb phrase: Kin sani yau babu aiki.
At the very beginning for emphasis on “today”:
- Yau, kin sani babu aiki? – Today, do you know there’s no work?

So yes, you can move yau, but the version you have is perfectly natural.

What does babu mean exactly in babu aiki?

Babu is an existential negative meaning roughly:

there is no / there isn’t / there are no

So:

babu aiki – there is no work / there isn’t work
babu ruwa – there is no water
babu mutane – there are no people

In your sentence:

yau babu aiki – today there is no work or more naturally there’s no work today.

The positive counterpart is akwai (there is/are):

akwai aiki – there is work
akwai aiki yau – there is work today

So you can think: akwai X = there is X; babu X = there is no X.

Is babu aiki a full sentence by itself?

Yes. Babu aiki can stand alone as a complete sentence:

Babu aiki. – There’s no work.

You can add time expressions:

Yau babu aiki. – There’s no work today.
Gobe babu aiki. – There’s no work tomorrow.

Or a place:

A ofis babu aiki. – At the office there’s no work.

In your longer sentence, yau babu aiki is a clause that acts as the thing known:

Ke kin sani [yau babu aiki]?
You know (that) [today there is no work]?

How would I say the opposite of yau babu aiki?

You normally switch babu to akwai:

Yau akwai aiki. – Today there is work.
Akwai aiki yau. – There is work today.

So your pair can be:

Yau akwai aiki. – there is work today
Yau babu aiki. – there is no work today

Does kin sani mean “do you know” or “did you know” or “have you known”?

Hausa aspect doesn’t match English tenses one‑to‑one. Kin sani is perfective/completive, and the exact English tense depends on context.

In this sentence, with yau (today) and the ongoing situation of “no work,” the most natural English is:

“Do you know there’s no work today?”

In another context, it could be:

“Did you know…?” (if you’re talking about knowledge at some earlier point)
“Have you realized…?”

So kin sani itself doesn’t force a strict past vs present the way English does; you let the rest of the sentence (and situation) guide the translation.

Is this sentence polite, casual, or rude? How would I make it sound more polite?

Ke kin sani yau babu aiki? is informal and can sound quite direct, especially with the emphatic ke. It’s fine among friends, co‑workers, or family, but might feel too sharp in a very polite or hierarchical situation.

Ways to soften or sound more polite/respectful:

Drop the emphatic ke:
- Kin sani yau babu aiki? – still direct, but less pointed.
Add something like kai / kuyi for respect (to older person or superior you pluralize):
- Kun sani yau babu aiki? – Do you (pl./polite) know there’s no work today?
Use a more indirect verb, like “hear (the news)” instead of “know”:
- Kin ji labari cewa yau babu aiki? – Have you heard that there’s no work today?
  This sounds softer and more polite.

The original is absolutely fine in everyday, equal‑status conversations.