Typing environment

In type theory a typing environment (or variable assignment) represents the association between variables names and data types. More formally an environment Γ is a set or ordered list of pairs ⟨ x , τ ⟩ , usually written as x : τ , where x is a variable and τ its type.

In statically typed programming languages these environments are used and maintained by type rules to type check a given program or expression.