minna no doui ga hituyou desu.

みんな means everyone or all the people involved, depending on context.

In this sentence, it refers to the group whose agreement is needed. So it is not just everything in a general sense; it means all the people.

Examples:

• みんなが来た。 = Everyone came.
• みんなの意見 = everyone’s opinions

Here, の connects みんな and 同意 and works like ’s or of in English.

So:

• みんなの同意 = everyone’s agreement = the agreement of everyone

This is a very common pattern:

• 私の本 = my book
• 先生の話 = the teacher’s story/talk
• みんなの同意 = everyone’s consent/agreement

同意 means agreement, consent, or approval, depending on context.

It is a noun. In this sentence, it means the agreement/consent of all the people involved.

A useful nuance:

• 同意 often has the feeling of consent or agreeing to something
• 賛成 more often means being in favor of an idea or proposal

So みんなの同意が必要です can sound more like we need everyone’s consent/agreement, not just everyone supports it.

が marks 同意 as the thing that is necessary.

So the structure is basically:

• みんなの同意 = everyone’s agreement
• が必要です = is necessary

Literally:

• Everyone’s agreement is necessary.

Japanese often builds sentences this way, where the thing being needed is marked with が.

Compare:

• お金が必要です。 = Money is necessary. / I need money.
• 時間が必要です。 = Time is necessary. / We need time.

So が is natural here because 同意 is the thing required.

必要 is usually treated as a na-adjective and also behaves a lot like a noun.

It means necessary or need.

In this sentence:

• 必要です = is necessary

You can also see it in other patterns:

• 必要なもの = a necessary thing
• 許可が必要です。 = Permission is necessary.
• それは必要ないです。 = That isn’t necessary.

So 必要 is not a verb meaning to need. Instead, Japanese expresses the idea more like X is necessary.

Japanese often expresses need with 必要です rather than with a direct verb equivalent to English need.

So instead of saying:

• We need everyone’s agreement

Japanese says:

• みんなの同意が必要です。
• Literally: Everyone’s agreement is necessary.

This is a very common Japanese way of expressing need.

There are verbs like 要る for needing things, but 必要です is very common and often sounds more formal or neutral in sentences like this.

です makes the sentence polite.

So:

• みんなの同意が必要です。 = polite
• みんなの同意が必要だ。 = plain
• みんなの同意が必要。 = very casual / clipped

Since 必要 is not a verb, です works like the polite copula here, similar to saying is in English.

Yes, but the nuance changes.

• みんなの同意が必要です。 focuses on everyone’s agreement as the thing that is needed.

• みんなの同意は必要です。 can sound more like as for everyone’s agreement, it is necessary, with more contrast or topic emphasis.

In many situations, が必要です is the most natural default pattern when saying that something is needed.

Yes. Japanese often leaves out subjects when they are understood from context.

So this sentence could mean things like:

• We need everyone’s agreement.
• Everyone’s agreement is necessary.
• It requires everyone’s consent.

The exact English subject depends on the situation. Japanese does not need to state it if it is already clear.

Yes. It is often written in hiragana as みんな, but it can also come from 皆.

You may see:

• みんな
• 皆
• 皆んな is possible but much less common

In everyday Japanese, みんな in hiragana is extremely common and natural.

Here are some common variations:

• みんなの同意が必要です。
  polite, standard

• みんなの同意が必要だ。
  plain style

• みんなの同意が必要。
  casual, shortened

More formal versions might be:

• 皆様の同意が必要です。
  more polite because 皆様 is more respectful than みんな
• 全員の同意が必要です。
  more formal or precise, meaning the consent of all members/everyone

So みんなの同意が必要です is natural, polite, and straightforward, but not especially formal.