sinrai ha daizi desu.

It is read:

しんらい は だいじ です。

A more natural way to write it, without learner spaces, is:

信頼は大事です。

Romanization:

shinrai wa daiji desu

Two useful pronunciation notes:

• は is written ha but pronounced wa when it is the topic particle.
• です is often pronounced something like des in everyday speech, although learners usually say desu at first.

信頼（しんらい） means trust or confidence in someone or something.

In this sentence, it is a noun.

Examples:

• 信頼がある = there is trust
• 信頼する = to trust

So in 信頼は大事です, 信頼 is the thing being talked about: trust.

Because は is acting as the topic particle, and when it is used as a particle, its pronunciation is wa, not ha.

This is one of the first unusual spelling/pronunciation points learners meet in Japanese.

So:

• は as a normal kana in a word: usually ha
• は as a particle: pronounced wa

In this sentence, 信頼は means as for trust or regarding trust.

は marks the topic of the sentence.

So 信頼は大事です is literally something like:

• As for trust, it is important.

Very often, natural English just becomes:

• Trust is important.

A key point: は does not always equal the English word is. It shows what the sentence is about.

This is a very common question.

In a basic explanation:

• は marks the topic
• が often marks the subject more directly or gives it more focus

So:

• 信頼は大事です。 = Trust is important. / As for trust, it is important.
• 信頼が大事です。 = Trust is what is important. / It is trust that is important.

The version with は sounds more like a general statement about trust. The version with が can sound more contrastive or more focused, depending on context.

For a simple standalone statement, 信頼は大事です is very natural.

Yes, 大事（だいじ） means important, and it behaves like a na-adjective in Japanese.

Japanese learners often learn two broad adjective groups:

• i-adjectives: like 高い
• na-adjectives: like 静か, 便利, 大事

大事 is in the na-adjective group.

In this sentence, it is being used at the end as the predicate:

• 信頼は大事です。

That is why there is no な here.

Because な is only used when a na-adjective comes directly before a noun.

Compare:

• 大事なこと = an important thing
• 大事な人 = an important person

But when the adjective is at the end of the sentence, you do not use な:

• そのことは大事です。
• 信頼は大事です。

So:

• before a noun: 大事な + noun
• at the end of a sentence: 大事です

です makes the sentence polite.

It is often called the copula, but for beginners the most useful idea is:

• it helps make a statement politely
• it often appears after nouns and na-adjectives

So:

• 信頼は大事だ。 = plain style
• 信頼は大事です。 = polite style

Both mean the same thing, but です is more appropriate in neutral polite speech, in class, with strangers, and in many everyday situations.

Yes. 大事 can also carry a nuance like:

• valuable
• precious
• serious
  depending on context.

For example:

• 大事な友だち = an important/precious friend
• 大事な話 = an important matter
• 大事にする = to treasure; to take good care of

In 信頼は大事です, the most natural meaning is simply:

• Trust is important.

Yes, it is natural and grammatically correct.

It sounds like a general statement, motto, or piece of advice:

• Trust is important.

It could appear in conversation, writing, teaching materials, or a speech.

Japanese normally would not use spaces, so the standard written form is:

信頼は大事です。

Yes. 大切（たいせつ） is another very common word meaning important, valuable, or precious.

So both are natural:

• 信頼は大事です。
• 信頼は大切です。

Very roughly:

• 大事 can feel a little more direct or conversational
• 大切 can feel a little softer or more heartfelt in some contexts

But in many situations, they are very close in meaning.

Japanese does not have articles like English a, an, and the.

So 信頼 can simply mean trust in a general sense, depending on context.

That is why 信頼は大事です naturally means:

• Trust is important

rather than needing something like:

• The trust is important
• A trust is important

Japanese lets context handle that kind of distinction.