Eng

Essential...

要

Ask for, Blackmail, Brief, Coerce, Demand, Engage, Essential, Examine, If, Important, In case, Investigate, Invite, Make an, Midriff, Necessary, Necessity, Need, Ought to, Require, Shall, Should, Stop, Summarize, Summary, Threaten, Waist, Want, Will

必備

Essential, Mandatory

必不可少

Essential

(Difficult, Forbidden, Hard, No, None, Not allowed)

不可或缺

Essential, Indispensable

(Difficult, Forbidden, Hard, No, None, Not allowed)

至關重要

Crucial, Essential, Extremely important, Vital

(Important)

要地

Essential, Strategic

十分必要

Essential, Necessary

(Complete, Completely)