What is "tautomer"

n. (context chemistry English) Any of the multiple forms of a tautomeric compound.

Tautomers are constitutional isomers of organic compounds that readily interconvert. This reaction commonly results in the relocation of a proton. Although it is a complicated concept, tautomerism is relevant to the behavior of amino acids and nucleic acids, two of the fundamental building blocks of life.

The concept of tautomerizations is called tautomerism. The chemical reaction interconverting the two is called tautomerization.