This is a new type of smartphone.

They (referring to women or girls) are my best friends.

He is acting in a way that is like 'hide the head but forget the tail'.

It was revealed that he had a hidden weapon.

He lied to conceal the truth.

He installed a hidden camera in the room.

Oh, that's right, I remembered what I ate for dinner yesterday.

It's not so much a big problem.

He is the ringleader of this plan.

He goes to the gym every day to train his tensor.