The symbol "λ" (lambda) is the 11th letter of the Greek alphabet. In mathematics and science, it is often used to represent various concepts, such as wavelength in physics, eigenvalues in linear algebra, and the decay constant in radioactive decay. In computer science, particularly in programming languages like Python and JavaScript, "lambda" refers to anonymous functions or expressions that can be defined without a name. These functions are useful for short, throwaway tasks, allowing for more concise and readable code.