essential

/i-ˈsen(t)-shəl/

adjective

  1. of, relating to, or constituting essence : inherent

  2. of the utmost importance : basic, indispensable, necessary

  3. being a substance that is not synthesized by the body in a quantity sufficient for normal health and growth and that must be obtained from the diet

essential fundamental vital cardinal mean so important as to be indispensable. essential implies belonging to the very nature of a thing and therefore being incapable of removal without destroying the thing itself or its character. fundamental applies to something that is a foundation without which an entire system or complex whole would collapse.

noun

  1. something basic

  2. something necessary, indispensable, or unavoidable

the essentials of astronomy

noun

  1. any of various amino acids that are required for normal health and growth in many vertebrates, are either not manufactured in the body or manufactured in insufficient quantities, are usually supplied by dietary protein, and include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine