[sobani]

How many of those languages can take an expression instead of a lambda?

Func<..> is lambda that can only be invoked.

Expression<Func..>> is an AST of a lambda that can be transformed by your code/library.

[Tyr42]

R let's you do that, and it gets used by the tidy verse libraries to do things like change the scope variables in the functions are looked up in.