Definition of uracil in US English:



  • A compound found in living tissue as a constituent base of RNA. In DNA its place is taken by thymine.

    A pyrimidine derivative; chemical formula: C₄H₄N₂O₂

    • ‘Several transformants were obtained by their ability to grow in minimal medium without uracil and uridine but supplemented with arginine.’
    • ‘Thymine, present in DNA, and uracil, present in RNA, also contribute to this band.’
    • ‘He and his group have found that folate deficiency breaks chromosomes due to massive incorporation of uracil into human DNA.’
    • ‘The nitrogen-containing units are the bases: adenine, cytosine, guanine, and uracil.’
    • ‘RNA has the same set of four bases, except that instead of thymine, RNA has uracil - commonly referred to as U.’


Late 19th century: from ur(ea) + ac(etic) + -il.