Joukkueen henki on hyvä.

Because joukkueen is the genitive singular of joukkue.

In this sentence, joukkueen means of the team or the team's. Finnish often shows possession by putting the possessor in the genitive:

• joukkueen henki = the team's spirit

A useful detail: the dictionary form is joukkue, but many Finnish nouns ending in -e use a stem with -ee- before endings:

• joukkue → joukkueen
• perhe → perheen

So the ending is not just random; it follows a common noun pattern.

Because henki is the main noun of the phrase, not the possessor.

In joukkueen henki:

• joukkueen = the possessor, so it takes the genitive
• henki = the thing being talked about, so it stays in the nominative here

The whole phrase joukkueen henki is the subject of the sentence, and subjects in this kind of sentence are normally in the nominative.

Because hyvä is a predicate adjective after on.

In sentences with olla (to be), the adjective is often in the nominative:

• Henki on hyvä.
• Sää on kaunis.
• Talo on iso.

So hyvä is not modifying joukkueen directly. It is describing the subject joukkueen henki through the verb on.

Yes, mainly with the subject in number.

Here the subject joukkueen henki is singular, so the adjective is singular too:

• Joukkueen henki on hyvä.

If the subject were plural, the adjective would usually be plural as well:

• Pelaajat ovat hyviä.

So hyvä does not match joukkueen just because joukkueen is nearby. It describes the whole subject phrase.

Because Finnish has no articles.

English needs words like the and a/an, but Finnish does not. Whether something is definite or indefinite is understood from context.

So Joukkueen henki on hyvä can naturally correspond to English with the:

• The team's spirit is good
• The team spirit is good

The exact English article depends on context, not on a separate Finnish word.

Here henki means something like:

• spirit
• morale
• atmosphere

So it is not about a literal breath or necessarily a ghost, even though henki can have other meanings in other contexts.

In a team context, henki usually refers to the mood or spirit within the group. So this sentence is about the team's internal atmosphere being good.

Yes. Joukkuehenki is a very common compound noun meaning team spirit.

So these are both possible:

• Joukkueen henki on hyvä.
• Joukkuehenki on hyvä.

The one-word compound joukkuehenki sounds a bit more like a fixed concept, while joukkueen henki can sound more like the spirit of the team in that specific case. In many situations, though, the difference is small.

Yes, and that is also very natural Finnish.

That version uses the adessive plus on to express possession:

• Joukkueella on hyvä henki. = The team has good spirit / good team spirit.

Compare:

• Joukkueen henki on hyvä.
  Focuses on the team's spirit as the subject.

• Joukkueella on hyvä henki.
  Focuses on the team having that good spirit.

Both are correct; the difference is mainly one of structure and emphasis.

Yes, Finnish word order is more flexible than English word order, but this sentence uses the most neutral order:

• Joukkueen henki on hyvä.

That is a normal subject + verb + predicate pattern.

You can change word order for emphasis, but then the sentence may sound more marked, literary, or context-dependent. For a learner, the version given is the safest and most natural basic pattern.

Very simply:

Question:

• Onko joukkueen henki hyvä? = Is the team's spirit good?

Negative:

• Joukkueen henki ei ole hyvä. = The team's spirit is not good.

In a yes/no question, Finnish usually puts -ko/-kö on the verb:

• on → onko

In a negative sentence, Finnish uses the negative verb ei:

• ei ole

Because the possessor is already clearly expressed by joukkueen.

Finnish can show possession in different ways, and here the genitive possessor is enough:

• joukkueen henki

You do not need an extra possessive suffix here. Possessive suffixes are especially common with pronoun possessors, for example:

• hänen henkensä = his/her spirit

But with a full noun like joukkueen, the plain genitive structure is the normal choice here.