Dynamic typing can forbid the latter (at runtime), but it's implementation dependent. There's a further distinction, Latent typing, which is where types are associated with values rather than variables.

But a dynamic language can have types associated with variables, and it can forbid changing those types after their types have been checked the first time.

> But a dynamic language can have types associated with variables, and it can forbid changing those types after their types have been checked the first time.

So, like C++ with `auto`?