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

Of the 20 different amino acids in proteins, nine are considered essential because the human body cannot make them directly and must obtain them from food. — Linda M. Boland, The Conversation, 21 Aug. 2026

Another quandary concerns how LUCA could have manufactured proteins as complicated as enzymes, which are made from many amino acids linked together in a particular sequence. — Philip Ball, Scientific American, 20 Aug. 2026

In Sustaera’s case, the company uses a solid sorbent made from an amino acid salt. — Emily Waltz, IEEE Spectrum, 19 Aug. 2026

Biocompatible pigments melt into skin for natural-looking coverage while amino acid powders absorb excess oil. — Celia Shatzman, Forbes.com, 18 Aug. 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