He installed a hidden camera in the room.

It was revealed that he had a hidden weapon.

He lied to conceal the truth.

Please be careful of his actual and hidden attitude.

The reason why the Earth revolves around the Sun is due to centripetal force.

He took a train to Tokyo in the allative case.

He converted to Christianity.

He is considering a career conversion.

Thinking sensibly, that plan will not succeed.

This ancient proverb, 'know the other side and yourself, and you will not be in danger in a hundred battles', teaches us the importance of understanding ourselves and others.