Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This

American Heritage Dictionary - Cite This Source - Share This

es·sen·tial       (ĭ-sěn'shəl)  Pronunciation Key  adj.   Constituting or being part of the essence of something; inherent. Basic or indispensable; necessary: essential ingredients. See Synonyms at indispensable. Medicine Of, relating to, or being a dysfunctional condition or a disease whose cause is unknown: essential hypertension. Biochemistry Being a substance that is required for normal functioning but cannot be synthesized by the body and therefore must be included in the diet: essential amino acids. n.   Something fundamental. Something necessary or indispensable. es·sen'ti·al'i·ty (-shē-āl'ĭ-tē), es·sen'tial·ness n., es·sen'tial·ly adv.

WordNet - Cite This Source - Share This

essential
adjective
1.	absolutely necessary; vitally necessary; "essential tools and materials"; "funds essential to the completion of the project"; "an indispensable worker"
2.	basic and fundamental; "the essential feature" [ant: inessential]
3.	of the greatest importance; "the all-important subject of disarmament"; "crucial information"; "in chess cool nerves are of the essence" [syn: all-important]
4.	being or relating to or containing the essence of a plant etc; "essential oil"
5.	defining rights and duties as opposed to giving the rules by which rights and duties are established; "substantive law" [syn: substantive] [ant: adjective]
noun
1.	anything indispensable; "food and shelter are necessities of life"; "the essentials of the good life"; "allow farmers to buy their requirements under favorable conditions"; "a place where the requisites of water fuel and fodder can be obtained" [syn: necessity] [ant: inessential]

American Heritage Stedman's Medical Dictionary - Cite This Source - Share This

essential es·sen·tial (ĭ-sěn'shəl)
adj.

1. Constituting or being part of the essence of something; inherent.
2. Basic or indispensable; necessary.
3. Of, relating to, or being a dysfunctional condition or a disease whose cause is unknown.
4. Of, relating to, or being a substance that is required for normal functioning but cannot be synthesized by the body and therefore must be included in the diet.

n.

1. Something fundamental.
2. Something necessary or indispensable.

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es·sen'ti·al'i·ty (-shē-āl'ĭ-tē) or es·sen'tial·ness n.

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

Essential

Es*sen"tial\, a. [Cf. F. essentiel. See Essence.]

1. Belonging to the essence, or that which makes an object, or class of objects, what it is.

Majestic as the voice sometimes became, there was forever in it an essential character of plaintiveness. --Hawthorne.

2. Hence, really existing; existent.

Is it true, that thou art but a a name, And no essential thing? --Webster (1623).

3. Important in the highest degree; indispensable to the attainment of an object; indispensably necessary.

Judgment's more essential to a general Than courage. --Denham.

How to live? -- that is the essential question for us. --H. Spencer.

4. Containing the essence or characteristic portion of a substance, as of a plant; highly rectified; pure; hence, unmixed; as, an essential oil. "Mine own essential horror." --Ford.

5. (Mus.) Necessary; indispensable; -- said of those tones which constitute a chord, in distinction from ornamental or passing tones.

6. (Med.) Idiopathic; independent of other diseases.

Essential character (Biol.), the prominent characteristics which serve to distinguish one genus, species, etc., from another.

Essential disease, Essential fever (Med.), one that is not dependent on another.

Essential oils (Chem.), a class of volatile oils, extracted from plants, fruits, or flowers, having each its characteristic odor, and hot burning taste. They are used in essences, perfumery, etc., and include many varieties of compounds; as lemon oil is a terpene, oil of bitter almonds an aldehyde, oil of wintergreen an ethereal salt, etc.; -- called also volatile oils in distinction from the fixed or nonvolatile.