Definition of essential :
1. Belonging to the essence, or that which makes an object, or class of objects, what it is.
2. Containing the essence or characteristic portion of a substance, as of a plant; highly rectified; pure; hence, unmixed; as, an essential oil.
3. Hence, really existing; existent.
4. Idiopathic; independent of other diseases.
5. Important in the highest degree; indispensable to the attainment of an object; indispensably necessary.
6. Necessary; indispensable; - said of those tones which constitute a chord, in distinction from ornamental or passing tones.
integral, meaty, inbred, requirement, necessity, no-frills, constituent, indwelling, inherent, primitive, constitutive, vital, native, infixed, quintessential, important, ingrained, ultimate, needful, substantial, natural, staple, inborn, surface, innate, inhering, intrinsic, be, constitutional, immanent, in essence, substantive, virtual, organic, of the essence, subjective, biogenic, all-important, congenital, inwrought, crucial, inseparable, life-sustaining, underlying, demand, internal
focal (part of speech: adjective)
existent (part of speech: adjective)
instrumental (part of speech: adjective)
pure (part of speech: adjective)
basic, irreducible, blameless, angelic, primal, pure, aboriginal, immaculate, formative, primary, undiluted, purebred, basal, honorable, elemental, unadulterated, spotless, uncluttered, innocent, unsullied, undefiled, unblemished, elementary, sinless, guiltless, simon-pure, stainless, monolithic, prime, nascent, faultless, austere, clear, stark, unadorned, white, unalloyed, virtuous, chaste, bare, decent, clean, atomic, untarnished, untainted, plain, indivisible, foundational, fundamental, simple
required (part of speech: adjective)
inevitable, must, compulsory, pressing, proviso, necessary, inescapable, mandatory, requisite, constraining, inexorable, obligatory, required, indispensable, prerequisite, stipulated, imperative, binding, involuntary
- And he so believed it to be, now, the only essential truth, or, at least, the half- truth that she had better believe in, that his smile had not a touch of bitterness. - "The Nest, The White Pagoda, The Suicide, A Forsaken Temple, Miss Jones and The Masterpiece", Anne Douglas Sedgwick.
- Water is an essential of life. - "Quiet Talks on Power", S.D. Gordon.
- Its essential truth to life sometimes makes one catch one's breath. - "Varied Types", G. K. Chesterton.