I depends on the language's architecture. 'var' and 'fun' might do exactly the same thing or they might be fundamentally different. I like languages where 'fun' is just syntax sugar for 'var'.
call, eval, () and numerous other mechanism exist in the wide universe of computer languages.
My own language is somewhat weird in that a function is an array of objects (procedure really), and declared the same way. applying an array of objects applies every one of them recursively, which will push them on the stack or recurse into them (call them). A quote object is used to contain an object as data that can't be called and won't be recursed. A kind of braindead hack related to a more elegant mechanism found in Lisp. The point of a quick overview of my own language which nobody else is likely to ever use is that there are so many viable programming languages out that that it's hard to make broad assumptions about how they should work or what conventions are correct for users of the language.