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

• 嘧啶类由嘧啶衍生出来或在结构上与嘧啶有关的一种基本混合物尤指核酸组成的尿嘧啶，胞嘧啶和胸腺嘧啶