それは秘密です。の英語

It's secret.

It's a secret.

It's secret.

This is a secret.

This is a secret.

I'll keep it a secret.

That is classified information.

It is an open secret.

Keep the secret.

My lips are sealed.

Is it a secret?

This is confidential mind.

That is being hidden in a hidden place.

an open secret

take the wraps off

Is it a secret?

The secret is [has got] out.

strictly in confidence

This information is confidential.

in secrecy

I know his secret.

keep it dark

The cat is out of the bag.

to disclose a secret to one―reveal a secret to one―divulge a secret to one―confide a secret to one―unbosom oneself of a secret to one―unburden one's heart of a secret to one―let one into the secret

in secrecy

Mind you, this is a secret.

of something, the state of being a secret

the state of something being secret

The secret got out.

to keep the matter （a） secret―preserve secrecy