uracil

American  

[yoor-uh-sil] / ˈjʊər ə sɪl /

noun

1. Biochemistry. a pyrimidine base, C 4 H 4 N 2 O 2 , that is one of the fundamental components of RNA, in which it forms base pairs with adenine. U

---

uracil British  

/ ˈjʊərəsɪl /

noun

1. biochem a pyrimidine present in all living cells, usually in a combined form, as in RNA. Formula: C 4 H 4 N 2 O 2

---

uracil Scientific  

/ yr′ə-sĭl /

1. A pyrimidine base that is a component of RNA. It forms a base pair with adenine during transcription. Uracil is therefore structurally analogous to thymine in molecules of DNA. Chemical formula: C ₄ H ₄ N ₂ O ₂ .

---

Etymology

Origin of uracil

1905–10; ur- ¹ + ac(etic) + -il, of uncertain origin

Compare meaning

How does uracil compare to similar and commonly confused words? Explore the most common comparisons:

• uracil vs. thymine
• uridine vs. uracil

Example Sentences

See Examples For:

uracil

By examining evolutionary relationships between uracil sensors and related sensory domains, the team found that ligand specificity can change relatively easily over time.

From Science Daily ● Feb. 8, 2026

Importantly they also discovered all five nitrogenous bases — adenine, guanine, cytosine, thymine, and uracil — that are necessary to build DNA and RNA.

From Salon ● Jan. 30, 2025

The researchers extracted uracil, niacin and some other organic compounds in the Ryugu samples by soaking the material in hot water and then performing analyses called liquid chromatography and high-resolution mass spectrometry.

From Reuters ● Mar. 21, 2023

“I am uncertain what it was finally, natural uracil or only dose or both,” he says.

From Science Magazine ● Jun. 18, 2021

The only difference in code between the gene’s original and the RNA copy was the substitution of the thymine to a uracil.

From "The Gene" by Siddhartha Mukherjee