[brandonbloom]

That's one definition of "typed", but not a very useful one. By that definition _everything_ is typed. That's an interesting metaphysics discussion worth having, but not relevant to explaining Forth to a C programmer.

Vanilla Forth values do not have runtime type information (such as class pointers or discriminator tags) nor does a traditional forth compiler have compile time type information (such as an abstracted understanding of the state of the stack at any given point of execution).

Meanwhile, Factor, a modern stack language has both: SmallTalk-style object-oriented class pointers on every value, and a compile-time stack-effect checker. Factor values have a Lisp-like dynamic typing discipline. That is to say "uni-typed" as "dynamic", or a discriminated union.