With water, colder and saltier equals denser. At the earth's poles, when water freezes, the salt doesn't necessarily freeze with it, so a large volume of dense cold, salt water is left behind. When this dense water sinks to the ocean floor, more water moves in to replace it, creating a current. The new water also gets cold and sinks, continuing the cycle. Incredibly, this process drives a current of water around the globe.
Medical Definition of HEART DISEASE. : an abnormal organic condition of the heart or of the heart and circulation.See heart disease defined for kids.ADVERTISEMENT.edical Definition of HEART DISEASE. : an abnormal organic condition of the heart or of the heart and circulation.
Definition of CHD. 1  Take the Heart Disease Quiz!  CHD: Congenital heart disease, a malformation of the heart or the large blood vessels near the heart. Congenital heart disease is the most frequent form of major birth defects in newborns affecting close to 1% of newborn babies (8 per 1,000). There are a great many types of congenital heart disease.