牛顿的运动定律是物理学中的基本原理。

Newton's laws of motion are fundamental ___principles in physics.

他始终坚持自己的原则，从不为了利益而妥协。

He always sticks to his ___principles and never compromises for personal gain.

牛顿的运动定律是经典物理学的基本原理。

Newton's laws of motion are fundamental ___principles in classical physics.

她从不撒谎，因为诚实是她生活的准则。

She never lies as honesty is one of her guiding ___principles.