1. (

• necessity ,
• essential ,
• requirement ,
• requisite ,
• necessary

) anything indispensable; "food and shelter are necessities of life"; "the essentials of the good life"; "allow farmers to buy their requirements under favorable conditions"; "a place where the requisites of water fuel and fodder can be obtained" ;

1. (

• essential ,
• indispensable

) absolutely necessary; vitally necessary; "essential tools and materials"; "funds essential to the completion of the project"; "an indispensable worker" ;

2. (

• essential

) basic and fundamental; "the essential feature" ;

3. (

• all-important ,
• all_important ,
• crucial ,
• essential ,
• of_the_essence

) of the greatest importance; "the all-important subject of disarmament"; "crucial information"; "in chess cool nerves are of the essence" ;

4. (

• essential

) being or relating to or containing the essence of a plant etc; "essential oil" ;

5. (

• substantive ,
• essential ,

) defining rights and duties as opposed to giving the rules by which rights and duties are established; "substantive law" ;