Complete dominance is a genetic concept where one allele completely masks the effect of another allele at the same gene locus. In this scenario, the dominant allele's traits are fully expressed in the organism, while the recessive allele's traits are not visible. For example, in Mendelian genetics, if a plant has one allele for purple flowers (dominant) and one for white flowers (recessive), the plant will display purple flowers. This phenomenon occurs in many organisms, including humans and animals. Complete dominance is a key principle in understanding inheritance patterns, as it helps predict the traits of offspring based on the alleles contributed by each parent.