cardinal

adj. /ˈkɑːrdɪnl/ C2

首要的；根本的

Most important; of fundamental importance.

仙境例句

The cardinal rule of the palace was never to laugh when the King's crown fell over his eyes.

王宫里最要紧的一条规矩是：国王的王冠滑下来遮住眼睛时，千万不能笑。