Adjective

(en adjective)

Equal to some requirement; proportionate, or correspondent; fully sufficient; as, powers adequate to a great work; an adequate definition lawfully and physically sufficient.

* De Quincey

Ireland had no adequate champion.

* Sir Arthur Conan Doyle, The Adventure of the Empty House

All day, as I drove upon my round, I turned over the case in my mind and found no explanation which appeared to me to be adequate .

Adjective

(en adjective)

Necessary.

Very important; of high importance.

* {{quote-magazine, date=2013-05-17

, author=George Monbiot, authorlink=George Monbiot , title=Money just makes the rich suffer , volume=188, issue=23, page=19 , magazine=(The Guardian Weekly) citation , passage=In order to grant the rich these pleasures, the social contract is reconfigured. The welfare state is dismantled. Essential public services are cut so that the rich may pay less tax. […]}}

Being in the basic form; showing its essence.

Don’t mind him being grumpy. That’s the essential Fred.

Really existing; existent.

* Webster (1623)

Is it true, that thou art but a name, / And no essential thing?

Such 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.

(medicine) Idiopathic.