s. absolutely necessary; vitally necessary
a. basic and fundamental
a. being or relating to or containing the essence of a plant etc
n. 要素, 要点, 本质
a. 必要的, 重要的, 本质的
[计] 本质冒险
1. Water is essential for life.
水对生命是必不可少的。
2. Good communication skills are essential in any job.
良好的沟通技巧在任何工作中都是必不可少的。
3. It is essential to eat a balanced diet for good health.
为了保持健康,均衡饮食是必不可少的。