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pyrimidine py·rim·i·dine (pī-rĭm'ĭ-dēn', pĭ-)
A crystalline organic base that is the parent substance of various biologically important derivatives.
Any of several basic compounds derived from or structurally related to pyrimidine, especially the nucleic acid constituents uracil, cytosine, and thymine.
Any of a group of organic compounds having a single six-member ring in which the first and third atoms are nitrogen and the rest are carbon. Pyrimidines include the bases cytosine, thymine, and uracil, which are components of DNA and RNA. Pyrimidine rings are also components of several larger compounds, such as thiamine and some synthetic barbiturates.