Lambda (uppercase ?, lowercase ?) is the 11th letter of the Greek alphabet. In the system of Greek numerals it has a value of 30. Letters that arose from Lambda include the Roman L and the Cyrillic letter El (?, ?).SymbolUpper-case letter ? The lambda particles in particle physics. The set of logical axioms in the axiomatic method of logical deduction in first-order logic. The cosmological constant. Used as a shield pattern by the Spartan army