any amino acid that is required by an animal for growth but that cannot be synthesized by the animal's cells and must be supplied in the diet.
Origin
1935-40
Examples from the web for essential amino acid
Two trials were also conducted to develop a test diet to determine essential amino acid requirements.
essential amino acid in Medicine
essential amino acidn. An alpha-amino acid that is required for protein synthesis but cannot be synthesized by humans and must be obtained in the diet.