/ˌɪn.dɪˈspen.sə.bəl/
If you say that someone or something is indispensable, you mean that they are absolutely essential and other people or things cannot function without them. 必不可少的
Cars have become an indispensable part of our lives.
汽车已成了我们生活中必不可少的一部分。
~ to sb/sth
She made herself indispensable to the department.
她成为这个部门不可缺少的一分子。
~ for sth/for doing sth
A good dictionary is indispensable for learning a foreign language.
一本好词典是学习外语必备的