It is hard to compare since Communism is a government political system and Capitalism is an economic system. Historically Republics have a economic system of Capitalism and Communist governments used...
Just to give a very short answer: Capitalism is a free market economy and is found in forms of government that range from a Republic (The United States) to Communism (China - though it is not true...
They are two entirely different concepts. A good example would be to site the USSR which its dictators described as a Communist organisation. In a Communist organisation the the work and assets means...