Infrequent ovulation. Pco is a congenital "defect" in the ovaries which causes infrequent ovulation. There are many degrees of pco and many other conditions which can be confused with it, .
Not a disease. Pcos is a syndrome - a constellation of problems which leads to infrequent periods, possibly hair growth in unwanted areas, hair loss from the scalp, and a predisposition to diabetes and lipid issues. It's a diagnosis of exclusion as other conditions may cause these symptoms and have to be eliminated before pcos is diagnosed.