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

Containing the essence or characteristic portion of a substance, as of a plant; highly rectified; pure; hence, unmixed; as, an essential oil.

Belonging to the essence or nature of a thing.

of the greatest importance; "the all-important subject of disarmament"; "crucial information"; "in chess cool nerves are of the essence"

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

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

A substance necessary for body function that cannot be produced by the body but must be obtained from food.

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"

Idiopathic; independent of other diseases.

Required for the normal growth of an organism but not synthesized by the organism.

A nutritional term applied to vitamins, minerals, and amino acids; refers to anything that the body does not manufacture and that must be obtained through the diet.

Necessary. In the context of nutrition, this refers to the basic food elements (fats and amino acids) which cannot be synthesized by the body. These substances are necessary for cellular metabolism and viability and are therefore an essential part of the daily diet.