Polygenic traits are characteristics influenced by two or more genes rather than a single gene. Because many genes contribute, these traits usually show continuous variation instead of simple Mendelian either-or patterns. Familiar examples include human height and skin color; many common health conditions such as heart disease and type 2 diabetes also have polygenic genetic components.
Environment often matters as well. When genes and environment both shape a trait, geneticists call it multifactorial. For a concise definition from the U.S. National Human Genome Research Institute, see NHGRI’s polygenic trait glossary entry.