necessary

adj

• ① 必要的,必需的
  • Most necessary things in life are free.人生必要的东西大部分都是免费的(如阳光、空气等)。
  • a necessary condition必要条件
  • Sunshine and water are necessary to plants.阳光与水对植物来说是必要的。
  • They prepared all the things necessary for the trip.他们准备了旅行所需的一切东西。
  • It is necessary to prepare for the worst.有必要做最坏的打算。
  • Is it necessary that you (should) be so strict with your students?你有必要对你的学生这么严厉吗?(★【口】多半不用should;此句可改写为: Is it necessary for you to be so strict with your students?)
  • I'll help you when [whenever] necessary.必要的时候,我会帮助你。
  • I will go, if necessary.必要的话,我会去。
  • It is necessary for you to attend the meeting.你有必要参加该会。
  • I don't want to say more than necessary.我不想多言。

• ②[无比较级]不可避免的
  • a necessary evil不可避免的恶事[弊害]