Definition of "essential"

Thus, research-based resources with the potential to assist teachers prepare secondary students for tertiary education are essential.

2018, Clarence Green, James Lambert, “Advancing disciplinary literacy through English for academic purposes: Discipline-specific wordlists, collocations and word families for eight secondary subjects”, in Journal of English for Academic Purposes, volume 35, page 105

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. […]

2013 May 17, George Monbiot, “Money just makes the rich suffer”, in The Guardian Weekly‎, volume 188, number 23, page 19

Or is it true, that thou art but a bare name, / And no eſſential thing?

1612–1613 (date written), John Webster, The Tragedy of the Dvtchesse of Malfy. […], London: […] Nicholas Okes, for Iohn Waterson, […], published 1623, Act III, scene ii

It is usually allowed that there is the natural body, as St. Paul called it, which is dissolved at death, and the etheric or spiritual body which survives and functions upon an etheric plane. Those are the essential things. But we may really have as many coats as an onion and there may be a mental body which may shed itself at any spot where great mental or emotional strain has been experienced.

1925 July – 1926 May, A[rthur] Conan Doyle, “In which Three Investigators Come across a Dark Soul”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019