Koripallojoukkueen valmentaja on nuori nainen, joka puhuu rauhallisesti.

Koripallojoukkueen is made of:

• kori = basket
• pallo = ball
• → koripallo = basketball (one compound word)
• joukkue = team
• → koripallojoukkue = basketball team
• koripallojoukkueen = of the basketball team (genitive singular)

The ending -en is the regular genitive singular ending for many Finnish nouns that end in -e:

• joukkue → joukkueen
• huone → huoneen (room → of the room)

Because koripallojoukkue is treated as one word, its genitive is:

• koripallojoukkue + en → koripallojoukkueen

So Koripallojoukkueen valmentaja literally means “the basketball team’s coach.”

Finnish doesn’t have articles (the, a, an). The same form can correspond to English “a coach” or “the coach”, depending on context.

• valmentaja = coach
• Koripallojoukkueen valmentaja = the coach of the basketball team / the basketball team’s coach
• nuori nainen = a young woman / the young woman

The definiteness/indefiniteness is understood from context and word order, not from extra words. In this sentence, it obviously refers to a specific coach and a specific woman, so in English we naturally translate with “the coach … is a young woman” (or “the coach … is a young lady/woman”).

Both nuori and nainen are in the nominative singular:

• nuori = young (nominative, singular)
• nainen = woman (nominative, singular)

In an “X is Y” sentence (a copular sentence), Finnish normally uses:

• Subject in nominative
  • on (is) + predicative in nominative

Here:

• Koripallojoukkueen valmentaja (subject; nominative overall phrase)
• on (is)
• nuori nainen (predicative; nominative)

You’d use another case, like the partitive, in different patterns (e.g. Hänestä tulee nuori nainen – She will become a young woman), but with “is” and a stable identity, nominative for the predicative is standard.

In Finnish, adjectives almost always come before the noun they modify:

• nuori nainen = young woman
• pitkä mies = tall man
• uusi auto = new car

The reverse order, nainen nuori, is not normal for a neutral description and would sound wrong or very marked/poetic in most contexts.

So the natural, basic order is:

[adjective] + [noun] → nuori nainen

joka is a relative pronoun meaning roughly “who/that/which”. It introduces a relative clause that describes the noun right before it.

• nainen, joka puhuu rauhallisesti
  = the woman who speaks calmly

Key points:

• joka refers back to nainen (a singular noun), so the verb is puhuu (3rd person singular).
• Finnish does not repeat the subject pronoun:
  
  • Correct: joka puhuu (who speaks)
  • Not: joka hän puhuu (“who she speaks”) – that’s wrong in this structure.

joka can refer to people, animals, or things:

• mies, joka… – the man who…
• kirja, joka… – the book that/which…

The comma marks the start of a relative clause. In Finnish:

• A clause introduced by joka is normally separated with a comma from the main clause.
• Here, “joka puhuu rauhallisesti” is extra information describing nainen.

So:

• Koripallojoukkueen valmentaja on nuori nainen, joka puhuu rauhallisesti.
  → main clause: Koripallojoukkueen valmentaja on nuori nainen.
  → relative clause: joka puhuu rauhallisesti.

Writing nuori nainen joka puhuu rauhallisesti without a comma is not standard in normal prose.

In Finnish, to say “speak in a [way]” / “speak calmly”, you use an adverb, not an adjective.

• Verb puhua = to speak
• Adjective rauhallinen = calm (as a quality: a calm person, a calm voice)
• Adverb rauhallisesti = calmly

Rule of thumb:

• Adjective (e.g. rauhallinen) describes nouns:
  
  • rauhallinen nainen = a calm woman
• Adverb (e.g. rauhallisesti) describes verbs or adjectives:
  
  • puhuu rauhallisesti = speaks calmly

So puhuu rauhallisesti is the correct way to express “speaks calmly.”

rauhallisesti is formed like many Finnish adverbs of manner:

• rauhallinen (calm, peaceful – adjective)
• Remove -nen, add -sesti / -sti
• → rauhallisesti = calmly, in a calm manner

rauhassa is the inessive case of rauha (peace):

• rauha = peace
• rauhassa = in peace, peacefully (often meaning “undisturbed, in peace and quiet”)

Typical uses:

• Hän puhuu rauhallisesti.
  He/She speaks calmly. (manner of speaking)
• Haluan työskennellä rauhassa.
  I want to work in peace / without being disturbed.

In your sentence, rauhallisesti fits better because it directly modifies the verb puhuu (how she speaks).

No, Valmentaja koripallojoukkueen is not natural Finnish. The genitive modifier usually comes directly before the noun it belongs to:

• Koripallojoukkueen valmentaja = the basketball team’s coach
• talon ovi = the door of the house
• ystäväni auto = my friend’s car

So:

• ✅ Koripallojoukkueen valmentaja on nuori nainen…
• ❌ Valmentaja koripallojoukkueen on nuori nainen…

You can move larger chunks (for emphasis or style), but you keep “[genitive] + [head noun]” together:

• Nuori nainen, joka puhuu rauhallisesti, on koripallojoukkueen valmentaja.
  = The young woman who speaks calmly is the coach of the basketball team.

The internal order [Koripallojoukkueen valmentaja] must remain.