要

necessary, needed, essential, indispensable, necessity, need, requirement

demand, firm request, requisition, requirement, desire

important, momentous, essential, principal, major

appeal, call for something, request, claim, demand, axiom

chief, main, principal, major

demand, request

demand for, request

necessity

main cause, primary factor

component, factor, item (e.g. in list), element (e.g. in array), member (e.g. data structure)