noun, plural: hearts
(2) That which resembles a heart in shape, i.e. a roundish figure with an obtuse point at one end and an indentation at the other end.
(3) A position relating to the mid or center, or that which is the most essential or vital part.
In mammals and birds, the heart consists of four chambers: right and left ventricles, and right and left atria. In reptiles and amphibians, the heart has only three chambers. In fish, the heart is composed of one auricle and one ventricle.