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Number & MeasureGreekEnglish

Lambda

/ˈlæmdə/noun

The eleventh letter of the Greek alphabet, used as a symbol for wavelength, decay constant and anonymous functions.

The Greek roots

λάμβδα
lámbda
the letter L

Literally: the letter lambda

Follow a root:λάμβδα1 word

The story of the word

The shape arrived from Phoenician lamed, an ox goad, and Greek straightened it into Λ. Spartan shields carried the letter for Λακεδαίμων, which is why film Spartans march behind a big lambda. Alonzo Church chose λ for his 1930s calculus of functions and later gave more than one account of why, including a shrug, so the typographic story about a stray caret is a guess rather than a record.

How it travelled
Phoenician → Ancient Greek → Latin → English

In a sentence

Wavelength is written as lambda in every optics textbook.

The whole file was three lambdas and a map call.

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