/ˈnesəsəri; US -serɪ ||; ˈnɛsəˌsɛrɪ/adj necessary (for sb/sth) (to do sth) that is needed for a purpose or a reason 必需的；必要的:
A good diet is necessary for a healthy life. 良好的饮食习惯对健康的生活是必需的。It's not necessary for you all to come. 你们不必全都来。If necessary I can take you to work that day. 必要的话，那天我可以送你去上班。 [OPP] unnecessary 反义词为unnecessary