amino acid

noun

: an amphoteric organic acid containing the amino group NH₂

especially : any of the various amino acids having the amino group in the alpha position that are the chief components of proteins and are synthesized by living cells or are obtained as essential components of the diet

Examples of amino acid in a Sentence

Recent Examples on the Web

Tryptophan is the amino acid your body converts into serotonin and, eventually, melatonin. — Patsy Anthony, Vogue, 19 Oct. 2026

What’s Happening Researchers are continuing to redesign peptides, the short chains of amino acids the body uses to signal, build muscle and regulate the immune system, so they can be swallowed rather than injected. — Samantha Agate, Kansas City Star, 16 Oct. 2026

Peptides are small chains of amino acids that serve as building blocks for proteins and help regulate muscle growth, hormone signaling, enzyme formation and immune function. — Samantha Agate, Miami Herald, 16 Oct. 2026

And a few are very highly specific, such as the protease that activates insulin, which only cuts near a very specific series of amino acids. — ArsTechnica, 14 Oct. 2026

Word History

First Known Use

1897, in the meaning defined above

Rhymes for amino acid

• antacid
• placid

Kids Definition

amino acid

noun

ami·​no acid

ə-ˈmē-nō-

: any of numerous acids that include some which are the building blocks of proteins and are made by living cells from simpler compounds or are obtained in the diet

Medical Definition

amino acid

noun

: an amphoteric organic acid containing the amino group NH₂

especially : alpha-amino acid