lambda /ˈlæm.də/ noun8 •The eleventh letter of the Classical and Modern Greek alphabet, the twelfth of the Old Greek alphabet. •Ellipsis of lambda expression. •Ellipsis of lambda function. •Unit representation of wavelength. •The cosmological constant. •Ellipsis of lambda baryon. •The percentage change in an option value divided by the percentage change in the underlying asset's price. •The junction of the lambdoid and sagittal sutures of the cranium. formslambdas