Eugenics: This is a movement aimed at improving the genetic composition of humans through controlled breeding, often associated with Social Darwinism due to its focus on 'improving' humanity's fitness.
Capitalism: An economic system where private entities own the means of production and operate for profit. It's related because Social Darwinists often use this theory to justify laissez-faire capitalism - let businesses compete without government interference.
Racism: Prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one's own race is superior. Racism can be justified through Social Darwinist beliefs by arguing some races are naturally superior.