definition of
essential

[1] #1 essential a. basic and fundamental; "the essential feature". wn

[2] #2 essential s. [all-important, all important, crucial, of the essence] of the greatest importance; "the all-important subject of disarmament"; "crucial information"; "in chess cool nerves are of the essence". wn

[3] #3 essential n. [necessity, 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". wn

[4] #4 essential a. being or relating to or containing the essence of a plant etc; "essential oil". wn

[5] #5 essential a. [substantive] defining rights and duties as opposed to giving the rules by which rights and duties are established; "substantive law". wn