These terms are often used synonymously, but they are not. Marx developed a whole body of scientific tenets not all of them are consistent with what has been executed by communist leaders. First of all, communism is in contrast to Marx’ dialectics itself which states that progress is the result of perpetually finding solutions to contradictions. According to the proponents of communism, communism is the solution of all social contradictions. Consequently, communism is the cessation of all social progress. Moreover, as life is a continuous adaptation to an ever changing environment, solution of all contradiction once and for ever spells death. Next, as all communist countries suffered from lack of progress, this worldwide failure of communism to thrive proved correct Marx’ thesis that contradictions are the engine of progress.
Conclusively, as Marx’ tenets have been partially proved and disproved it is typical science and Marxism can be distinguished from the tenet of communism that hat been proved entirely wrong, theoretically and practically.