necessary necessary /ˈnɛsəˌsɛri/

adjective

1. () Absolutely essential  ( necessary )
   absolutely essential
     A good night's sleep is necessary for overall health.
   A good night's sleep is necessary for overall health.
   
2. () Unavoidably determined by prior circumstances  ( necessary )
   unavoidably determined by prior circumstances
    The necessary consequences of one's actions
   the necessary consequences of one's actions
   

noun

1. Anything indispensable  ( necessary , requisite , essential , necessity , requirement )
   anything indispensable
    Food and shelter are necessities of life
   food and shelter are necessities of life
    The essentials of the good life
   the essentials of the good life
    Allow farmers to buy their requirements under favorable conditions
   allow farmers to buy their requirements under favorable conditions
    A place where the requisites of water fuel and fodder can be obtained
   a place where the requisites of water fuel and fodder can be obtained