"優性" (yūsei) refers to the concept of "dominance" in genetics, where one allele masks the expression of another allele at the same locus. This means that if an individual has one dominant allele and one recessive allele for a trait, the dominant trait will be expressed in the phenotype. In the context of inheritance, dominant traits can be passed down from parents to offspring. For example, in the case of Mendelian inheritance, traits such as flower color in pea plants can be influenced by dominant and recessive alleles, illustrating how certain characteristics are inherited.