Definitions
1.nounA necessary ingredient.
2.nounA fundamental ingredient.
3.adjectiveNecessary.
4.adjectiveVery important; of high importance.
5.adjectiveNecessary for survival but not synthesized by the organism, thus needing to be ingested
6.adjectiveBeing in the basic form; showing its essence."Don’t mind him being grumpy. That’s the essential Fred."
7.adjectiveReally existing; existent.
8.adjectiveSuch that each complementary region is irreducible, the boundary of each complementary region is incompressible by disks and monogons in the complementary region, and no leaf is a sphere or a torus bounding a solid torus in the manifold.
9.adjectiveIdiopathic.