Learn Hardcore Finnish: Voisitko sinäkin kääntää yhden lauseen?

It’s the yes/no question clitic. Attaching -ko/-kö to a word (usually the verb) turns the clause into a polar question. Vowel harmony decides the form: back vowels (a, o, u) take -ko, front vowels (ä, ö, y) take -kö; i and e are neutral. Hence voisit + ko → voisitko.

Why is it voisitko instead of voitko?

Voisitko (conditional) makes the request more polite, like English “could/would you.” Voitko is more direct “can you/are you able to” and can feel brusquer, though not necessarily rude. For extra politeness you might see forms like Viitsisitkö… (“Would you mind…”) or Olisitko ystävällinen ja… (“Would you be so kind as to…”).

Do we really need the pronoun sinä here?

Finnish usually drops subject pronouns, but you keep sinä because -kin must attach to the word it modifies. Without sinä, you can’t say “you too” via -kin; you’d need something like myös sinä.

What does -kin in sinäkin mean?

It’s an additive clitic meaning “also/too,” and sometimes “even.” Placing it on sinä gives “you too” (or, in some contexts, “even you”). The word that bears -kin is the one being added/focused.

Can -kin go on other words, and how does that change the meaning?

Yes; it focuses whatever it’s attached to.

Voisitko sinäkin kääntää yhden lauseen? = you too (as well as others).
Voisitko sinä kääntää yhden lauseenkin? = one sentence too (in addition to something else), or “even one sentence,” depending on context.
Voisitko sinäkin kääntää tämänkin lauseen? = also this sentence (in addition to other sentences).

Why is it yhden lauseen, not yksi lause?

Objects of intended, bounded/complete actions take the total object, which for singular nouns is genitive -n: lause → lauseen. The numeral yksi behaves like an adjective and agrees in case with the noun, so genitive yhden lauseen (cf. nominative yksi lause, partitive yhtä lausetta).

Could it be yhtä lausetta instead?

Yes, but that’s partitive, which signals an unbounded/partial action. Voisitko kääntää yhtä lausetta suggests translating part of a sentence or translation in progress. For “translate one (whole) sentence,” yhden lauseen is the default.

Why does lause become lauseen?

It’s the regular genitive of many -e nouns: they take -en in the genitive. Examples: lause → lauseen, huone → huoneen, kirje → kirjeen.

Do I need yksi at all? Could I just say kääntää lauseen?

You can. Finnish has no articles, so lauseen can mean “a sentence” or “the sentence” from context. Adding yhden highlights the quantity “one (single) sentence,” often useful when sharing tasks.

Can I use myös instead of -kin? Difference between sinäkin and myös sinä?

Both mean “also/too.” Sinäkin is compact and very natural; myös sinä is equally correct and a bit more neutral. Position changes focus:

Voisitko sinäkin kääntää… = you too.
Voisitko myös kääntää… = also translate (in addition to something else).
Voisitko myös sinä kääntää… = you also.

What form is kääntää, and why this form?

It’s the 1st infinitive (dictionary form). After the modal voida (can/could), Finnish uses the bare infinitive: voisitko kääntää… “could you translate…”.

Could I say Kääntäisitkö sinäkin yhden lauseen? instead?

Yes. That applies the conditional to the main verb rather than using voida. It’s equally polite—more like “Would you translate one sentence?”

Does kääntää only mean “translate,” or also “turn”?

Both. Context tells which is meant. For languages, use essive for the target language and typically elative for the source:

kääntää suomeksi/englanniksi (into Finnish/English)
kääntää englannista suomeksi (from English into Finnish)

How do I add “for me/us” to the request?

Use the allative -lle:

Voisitko sinäkin kääntää minulle yhden lauseen?
Voisitko sinäkin kääntää meille yhden lauseen?

How would I answer this politely in Finnish?

Yes: Totta kai. Voin. / Voisin.; Toki.; Selvä.
No: Valitettavasti en voi. (Present en voi is natural even if the question used conditional; en voisi tends to sound hypothetical.)

Can I drop -ko and rely on intonation, like in English?

In casual speech, yes: Voisit säkin kääntää yhen lauseen? In standard writing, keep -ko/-kö.

Can I put -ko/-kö on another word for emphasis?

Yes; it then questions/emphasizes that word:

Sinäkö kääntäisit yhden lauseen? = “You would translate a sentence?” (surprised/contrastive) For a neutral polite request, voisitko is the norm.

Does sinäkin always mean “you too,” or can it mean “even you”?

It can mean either. -kin is additive, but in context it often shades into “even”: Sinäkin voit onnistua = “Even you can succeed.” Tone and context decide.

How do I say this to plural or formally addressed “you”?

Use te with conditional:

Plural: Voisitteko tekin kääntää yhden lauseen?
Formal singular (teitittely): the same form; in very formal writing you might capitalize: Voisitteko Te kääntää…

Is lause the right word for “sentence”? What about virke?

In school grammar, virke is an orthographic sentence (ends with . ? !), while lause is a clause. In everyday usage, people commonly say lause to mean a sentence, so your example is natural. Use virke if you specifically mean a written sentence unit.

How do I say “only one sentence”?

Add vain or ainoa:

Voisitko sinäkin kääntää vain yhden lauseen?
Emphatic: … yhden ainoan lauseen?