adj.
1.absolutely necessary
2.basic and fundamental
3.of the greatest importance
4.being or relating to or containing the essence of a plant etc
5.applying to essential legal principles and rules of right
6.absolutely required and not to be used up or sacrificed essential n.
1.anything indispensable
Idiom of the Day
buy up (something) or buy (something) up
to buy the total amount of something
The customers bought up all of the products.