Indispensable; essential; something that is absolutely necessary and cannot be omitted.
正しい道具は仕事をする上で不可欠だ。
The right tools are indispensable for doing the job.
信頼はチーム運営において不可欠な要素だ。
Trust is an indispensable element in team management.
この工程には専門知識が不可欠で、外部の協力が必要だ。
Specialized knowledge is essential for this process, and outside cooperation is needed.