- A family of 6-membered heterocyclic compounds occurring in nature in a wide variety of forms. They include several nucleic acid constituents (cytosine, thymine, and uracil) and form the basic structure of the barbiturates.
Definition from: MeSH via Unified Medical Language System at the National Library of Medicine
- A nitrogen-containing, single-ring, basic compound that occurs in nucleic acids. The pyrimidines in DNA are cytosine and thymine; in RNA, cytosine and uracil.
Definition from: Human Genome Project Information
at the U.S. Department of Energy
See also Understanding Medical Terminology.