py·rim·i·dine   (pī-rĭm'ĭ-dēn', pĭ-)    n.   A single-ringed, crystalline organic base, C4H4N2, that forms uracil, cytosine, or thymine and is the parent compound of many drugs, including the barbiturates. Any of several organic compounds derived from or structurally related to pyrimidine, especially the nitrogen bases uracil, cytosine, and thymine. [Alteration of pyridine.]

Main Entry: py·rim·i·dine
Pronunciation: pI-'rim-&-"dEn, p&-
Function: noun
1 : a weakly basic organic compoundC₄H₂N₂ of penetrating odor that is composed of a single six-membered ring having four carbon atoms with nitrogen atoms in positions one and three
2 : a derivative of pyrimidine having its characteristic ring structure; especially : a base (as cytosine, thymine, or uracil) that is a constituent of DNA or RNA

pyrimidine py·rim·i·dine (pī-rĭm'ĭ-dēn', pĭ-)
n.

1. A crystalline organic base that is the parent substance of various biologically important derivatives.

2. Any of several basic compounds derived from or structurally related to pyrimidine, especially the nucleic acid constituents uracil, cytosine, and thymine.