Definition of essential

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