lambda is the 11th letter of the greek alphabet. in the system of greek numerals lambda has a value of 30. the letter is widely used in mathematics, astrophysics, crystal optics, neurobiology, electrochemistry and cosmology. the greek alphabet has an important role in the nomenclature of astronomical bodies and subatomic particles. . lambda is the 11th letter of the greek alphabet. in the system of greek numerals lambda has a value of 30. the letter is widely used in mathematics, astrophysics, crystal optics, neurobiology, electrochemistry and cosmology. the greek alphabet has an important role in the nomenclature of astronomical bodies and subatomic particles.