Definition from Wiktionary, the free dictionary
- (evolutionary biology) A process by which heritable traits conferring survival and reproductive advantage to individuals, or related individuals, tend to be passed on to succeeding generations and become more frequent in a population, whereas other less favourable traits tend to become eliminated.
- (quantitative genetics) A process in which individual organisms or phenotypes that possess favourable traits are more likely to survive and reproduce: the differential survival and reproduction of phenotypes.
Related terms 
an evolutionary process