Stellar abundance refers to the composition of elements found in stars, particularly the amounts of various chemical elements compared to hydrogen and helium. This composition is crucial for understanding the formation and evolution of stars, galaxies, and the universe itself. Astronomers measure stellar abundance using spectroscopy, which analyzes the light emitted or absorbed by stars to identify the elements present. Different stars have varying stellar abundances, influenced by their age and the material from which they formed. For example, older stars, like those in globular clusters, often have lower abundances of heavier elements compared to younger stars in regions like the Milky Way. This variation helps scientists trace the history of element formation through processes such as nucleosynthesis in stars and supernovae.