F# is a statically typed language with gradual typing and full type inference.

Given

  let hello value =
      printfn "%A" value
    
  hello "world"
  hello 2

The binding "hello" has "'a -> unit" signature where 'a is a generic argument it accepts because the "printfn" binding with a given format specifier is generalized the same way and an unconstrained 'T (here 'a) is the most narrow type inferred for "hello".