Capitalism is a form of commodity production of competing Capital Owners that pay wage laborers to sell commodities on a market, seeking further and further accmulation.

Capitalism tends to monopolize into syndicates and eliminate its own competition. This doesn't mean it isn't still Capitalism, just that it's becoming Imperialism, ie moribund Capitalism, and that it is becoming ripe for central planning and public siezure. Capitalism develops towards Socialism, once the proletariat siezes control.