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

Peptides, for instance, are druglike chains of amino acids that have been widely promoted by celebrities and influencers as a way to build muscle and look younger, although there’s little science supporting their use. —ABC News, 27 Mar. 2026

Each formula contains a unique combination of antioxidants, vitamins, minerals, phytonutrients, amino acids and prebiotic fiber. —Noor Lobad, Footwear News, 26 Mar. 2026

That slightly sweet sap is packed with natural moisturizing factors—like amino acids, PCA, and hyaluronic acid—that keep skin hydrated and balanced. —Christa Joanna Lee, Allure, 26 Mar. 2026

These amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine – collectively necessary for building muscle, producing enzymes and hormones and maintaining healthy tissue. —Daryl Austin, USA Today, 21 Mar. 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