Functioning and Essential

noun

• Process or manner of functioning or operating.
  • usage: "the power of its engine determines its operation"; "the plane's operation in high winds"; "they compared the cooking performance of each oven"; "the jet's performance conformed to high standards"
  • synonyms: operation, performance

verb

• Perform as expected when applied.
  • usage: "The washing machine won't go unless it's plugged in"; "Does this old car still run well"; "This old radio doesn't work anymore"
  • synonyms: function, work, operate, go, run
• Serve a purpose, role, or function.
  • usage: "The tree stump serves as a table"; "The female students served as a control group"; "This table would serve very well"; "His freedom served him well"; "The table functions as a desk"
  • synonyms: serve, function
• Perform duties attached to a particular office or place or function.
  • usage: "His wife officiated as his private secretary"
  • synonyms: officiate, function

adjective

• Performing or able to perform its regular function.
  • usage: "a functioning flashlight"

noun

• Anything indispensable.
  • usage: "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"
  • synonyms: necessity, requirement, requisite, necessary

adjective

• Absolutely necessary; vitally necessary.
  • usage: "essential tools and materials"; "funds essential to the completion of the project"; "an indispensable worker"
  • synonyms: indispensable
• Basic and fundamental.
  • usage: "the essential feature"
• Of the greatest importance.
  • usage: "the all-important subject of disarmament"; "crucial information"; "in chess cool nerves are of the essence"
  • synonyms: all-important, all important, crucial, of the essence
• Being or relating to or containing the essence of a plant etc.
  • usage: "essential oil"
• Defining rights and duties as opposed to giving the rules by which rights and duties are established.
  • usage: "substantive law"
  • synonyms: substantive

• (a.) Hence, really existing; existent.
• (a.) Belonging to the essence or that which makes an object or class of objects, what it is.
• (a.) Important in the highest degree; indispensable to the attainment of an object; indispensably necessary.
• (a.) Necessary; indispensable; -- said of those tones which constitute a chord, in distinction from ornamental or passing tones.
• (a.) Idiopathic; independent of other diseases.
• (a.) Containing the essence or characteristic portion of a substance, as of a plant; highly rectified; pure; hence, unmixed; as, an essential oil.