Typing environment

In type theory, a typing environment (or typing context) represents the association between variable names and data types. More formally, an environment Γ{\displaystyle \Gamma } is a set or ordered list of pairs ⟨x,τ⟩{\displaystyle \langle x,\tau angle }, usually written as x:τ{\displaystyle x:\tau }, where x{\displaystyle x} is a variable and τ{\displaystyle \tau } its type.