adj. & n.
--adj.
1. absolutely necessary; indispensable.
2 fundamental, basic.
3 of or constituting the essence of a person or thing.
4 (of a disease) with no known external stimulus or cause; idiopathic.
--n. (esp. in pl.) a basic or indispensable element or thing.
Phrases and idioms:
essential element any of various elements required by living organisms for normal growth. essential oil a volatile oil derived from a plant etc. with its characteristic odour.
Derivatives:
essentiality n. essentially adv. essentialness n.
Etymology: ME f. LL essentialis (as ESSENCE)