A lambda abstraction is an abstract lambda expression . It is expressed in the language of lambda calculus. A lambda abstraction is to a functional programming language such as Scheme what pseudo-code is to an imperative programming language.

More specifically, a lambda abstraction is a lambda expression with no free variables: each its variables is bound by some lambda. E.g.

f (f (f x))

is a concrete lambda expression, whereas

λf. λx. f (f (f x))

is an abstract lambda expression.

For example, λ could stand for 'for each', 'for some', or 'there is'. In this case, the expression could stand for a 'logic proposition'.