lambda (general definition)

 Lambda, the 11th letter of the Greek alphabet, is the symbol for wavelength. In optical fiber networking, the word lambda is used to refer to an individual optical wavelength.

In mathematics and computer programming, the Lambda symbol is used to introduce "anonymous functions." Lambda notation distinguishes between variables used as mathematical arguments and variables that stand for predefined values. The use of the Lambda symbol in this sense was introduced by Alonzo Church in his theory of Lambda calculus in the 1930s.

Amazon Web Services offers a service called AWS Lambda that lets customers run code without having to worry about provisioning or managing servers. AWS Lambda has an event-driven architecture that executes code only when needed and scales automatically. Subscribers pay only for the compute time they consume and are not charged for time when their code is not running.