principal act主要行为principaladj.主要的；首要的n.本金；资本；校长；主角；委托人；主犯Principal stress's directionPrincipal Surface Combatants主要水面作战舰艇principal lines of direction主方向线principal sympathetic neuron主交感神经元Principal Distribution Depot主要分发仓库principal section of crystal晶体主截面principal maintenance period基本维修周期principal hor-izontal line主水平线principal axes of elasticity弹性主轴principal curvature function主曲率函数