< Lambda Calculus  
        
      Axioms
The first concept is that of abstraction. It is analogous to defining a function.
- λx.M
 
This defines a function which takes an argument x and returns a term M. Functions in lambda calculus have no name.
The second concept is that of invocation. It is essentially a function call.
- M N
 
This binds the argument N to the term M
Definitions
- Term
 - A term in Lambda calculus is a defined function. A term may contain variables.
 - Variable
 - A variable, may represent any term. A term may contain free variables or bound variables
 - Bound variables
 - A bound variable is a variable which will be bound to some term passed as an argument. Eg, In λx.xy, x is a bound variable.
 - Free variables
 - A free variable is any variable in a term which is not bound to some other term. Eg, In λx.xy, y is a free variable.
 
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