From Late Latin essentiālis, from Latin essentia.

• IPA: /ɪˈsɛn.ʃəl/, [əˈsɛn.tʃəl]

essential

1. Necessary.

   Synonyms: indispensable, Thesaurus:requisite

   Antonyms: accidental, accessorial, incidental, unnecessary, unneeded

   • 1941, Theodore Roethke, “Feud”, in Open House; republished in The Collected Poems of Theodore Roethke, 1975, →ISBN, page 4:

     There’s canker at the root, your seed
     Denies the blessing of the sun,
     The light essential to your need.
     Your hopes are murdered and undone.

2. Very important; of high importance.

   Synonyms: crucial, Thesaurus:important

   Antonyms: unimportant, Thesaurus:insignificant

3. (biology) Necessary for survival but not synthesized by the organism, thus needing to be ingested.
4. Being in the basic form; showing its essence.

   Synonyms: Thesaurus:intrinsic, Thesaurus:bare-bones

   Antonyms: adscititious, Thesaurus:extrinsic

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

5. Really existing; existent.

   Synonyms: Thesaurus:existent

   Antonyms: Thesaurus:inexistent

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

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

6. (geometry) 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.

7. (medicine) Idiopathic.

   essential blepharospasm

8. Having the nature of essence; not physical.
   • 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:

     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.

• inessential, unessential, non-essential, nonessential

• German: essenziell, notwendig, unverzichtbar
• Italian: necessario, indispensabile
• Portuguese: essencial
• Russian: необходи́мый
• Spanish: esencial

• French: indispensable
• German: wesentlich, unentbehrlich, unverzichtbar
• Italian: essenziale, fondamentale
• Portuguese: essencial
• Russian: ва́жный

• French: essentiel, fondamental
• Italian: essenziale, sobrio
• Portuguese: essencial, fundamental
• Russian: основно́й

essential (plural essentials)

1. A necessary ingredient.

   Synonyms: must-have

2. A fundamental ingredient.

• essentials
• essence