What does the "Lambda" in "Lambda calculus" stand for?

Question Detail: 

I've been reading about Lambda calculus recently but strangely I can't find an explanation for why it is called "Lambda" or where the expression comes from.

Can anyone explain the origins of the term?

Asked By : Pickle
Best Answer from StackOverflow

Question Source : http://cs.stackexchange.com/questions/55917

Answered By : Anton Trunov

An excerpt from History of Lambda-calculus and Combinatory Logic by F. Cardone and J.R. Hindley(2006):

By the way, why did Church choose the notation "$\lambda$"? In [Church, 1964, §2] he stated clearly that it came from the notation "$\hat{x}$" used for class-abstraction by Whitehead and Russell, by first modifying "$\hat{x}$" to "$\wedge x$" to distinguish function abstraction from class-abstraction, and then changing "$\wedge$" to "$\lambda$" for ease of printing. This origin was also reported in [Rosser, 1984, p.338]. On the other hand, in his later years Church told two enquirers that the choice was more accidental: a symbol was needed and "$\lambda$" just happened to be chosen.

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