"必须的" 的英语短语是 "necessary"。

"Necessary" 来自拉丁语 "necessarius"，意思是 "必要的"。它是形容词，指 "必要的" 或 "不可缺少的"。

例句：

It is necessary to bring an umbrella with you in case it rains. (你必须带上雨伞，以防下雨。)
Water is necessary for human survival. (水对人类的生存是必要的。)
It is necessary to finish the project on time. (必须按时完成这个项目。)
It is not necessary to attend the meeting if you are not feepng well. (如果你感觉不舒服，可以不用参加会议。)