adjective

1. of or constituting the intrinsic, fundamental nature of something; basic; inherent an essential difference
2. absolute; complete; perfect
3. absolutely necessary; indispensable; requisite
4. containing, or having the properties of, a concentrated extract of a plant, drug, food, etc. an essential oil
5. Biochem. needed for life or health but not synthesized within the body, as an amino acid or vitamin that must be consumed

Etymology: ME essencial < LL essentialis: see essence

noun