When traits are controlled by three or more genes, they are called polygenic traits, and their inheritance is called polygenic inheritance. Human skin color is a classic example following polygenic inheritance as the skin colour is regulated by three pairs of genes. Polygenic inheritance is influenced by the environment as well and not just the polygenes.

If 5 polygenes are there to control a character the number of phenotypes will be $2\times 5+1=11$ .