# System F and recursive types
In the simply-typed lambda calculus, we write types like <code>σ
# System F and recursive types
In the simply-typed lambda calculus, we write types like <code>σ
OCaml has type inference: the system can often infer what the type of
an expression must be, based on the type of other known expressions.
OCaml has type inference: the system can often infer what the type of
an expression must be, based on the type of other known expressions.