The variable R is used as the universal gas constant primarily due to its historical significance and standardization in scientific literature. The choice of R stems from its association with the word "regnault," named after the French scientist Henri Regnault, who contributed to the study of gases. Additionally, R represents a consistent value that simplifies calculations in the ideal gas law and thermodynamics. Understanding its derivation and significance can enhance comprehension of gas behavior in various conditions. Engaging with the concepts behind R will facilitate deeper insights into its application in gas-related equations.