More practical example: CPython vs. PyPy. Also applies to CPython and CRuby vs. their JVM and CLR counterparts like Jython, IronPython, JRuby, etc.
However, a language will impose some limitations on the implementation, be it a compiler or an interpreter. Dynamic typing is perhaps the most concrete example of this.
The idea of a 'fast language' is still nonsense, given how much faster the best interpreters of dynamic languages are compared to the code generated by the worst compilers of static languages.
However, a language will impose some limitations on the implementation, be it a compiler or an interpreter. Dynamic typing is perhaps the most concrete example of this.