What is the meaning of Λ?

wavelength

Half-life

Lebesgue measure

Lambda abstraction

a voiced alveolar lateral affricate (IPA [d͡ɮ]).

Lower-case lambda (λάβδα), the 11th letter of the ancient Greek alphabet. It represented the alveolar lateral approximant /l/. It is preceded by κ and followed by μ.

The lower case letter lambda (λάμδα), the eleventh letter of the modern Greek alphabet.

The number thirty in Greek numerals.

The number 30,000 in Greek numerals.

Source: wiktionary.org