Polygenic

Polygenic is a common adjective in genetics. It means "many genes". It is used when a genetic character (phenotypic trait) depends on more than one gene. 
It is very common and normal for a person's weight, for example, to depend on many causes, both genetic (inherited) and non-genetic (e.g. way of life). Here the use of polygenic means that various genes influence the weight of a person, as well as the non-genetic factors (life-style). The branch of genetics which studies polygenes is called quantitative genetics.