epistasis

This term is used exclusively within the fields of genetics and molecular biology to describe a specific type of gene interaction. It describes a hierarchical relationship where a "masking" gene overrides the phenotypic expression of another gene, regardless of the second gene's own alleles.

Because it is a specialized scientific term, it is almost never encountered in casual conversation. It is typically used in academic papers, textbooks, and clinical reports to explain complex inheritance patterns that do not follow simple Mendelian rules.