If I were to expand the post below, I'd add a rant about how capitalism is a completely artificial term as well as being impossibly hard to use. It's just a description of how things work, very naturally, in a free society, and could be seen in the ancient and medieval worlds too (except where feudalism was quite absolute); it's not a system. Unless of course you use it to mean our particular situation in which we're so lamentably removed from the concrete products of our work, in which case the confusion is multiplied.
"Capitalism" was first used, according to the OED, in the 1850s by Thackeray. Then the Marxists took it and ran with it.